The War of the Currents
Edison, Westinghouse, Tesla, and the Fight Over AC and DC
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Chapter topics include arc lighting experiments, the spread of AC power, safety concerns about electrical systems, and Edison's anti-AC campaigns. The conflict escalated when executions by electric chair linked alternating current with Westinghouse. Harold Brown's dramatic demonstrations and later collusion with Edison revealed the extent of the propaganda war.
The war ended with the Niagara Falls project choosing alternating current for its massive power generation. This decision effectively settled the debate between AC and DC systems. Anyone interested in how electrical power shaped modern civilization will find this account compelling.
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By the late 1870s, cities were starting to install arc lamp systems, powered by central generating plants. These systems used high voltages—above 3,000 volts—to light streets, factory yards, or the interiors of large buildings. The lamps were connected in series, and some ran better on alternating current.
In 1880, the Brush Electric Company installed a large-scale arc lighting system in New York City, setting up a central station to power a 3.2-kilometer stretch of Broadway with a 3,500-volt demonstration system. This early form of electric lighting came with serious drawbacks: it required constant maintenance, produced buzzing and flickering light, posed fire risks, was only practical for outdoor use, and, due to the high voltages involved, was dangerous for workers to handle.
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In 1878, inventor Thomas Edison identified a market for electric lighting that could reach customers' homes and businesses directly, filling a gap left by arc lighting systems. By 1882, he had formed the investor-owned utility Edison Illuminating Company in New York City. His system used direct current at 110 volts to power an incandescent lamp he had invented, competing against gas utilities. The company spread across the U.S., making Edison's direct current standard while controlling all technical development and patents. Direct current worked well with incandescent lamps, which were the main load of the time, and also supported storage batteries for backup and load-leveling. Generators could be easily connected in parallel, improving efficiency and reliability. Edison had also invented a meter that only worked with direct current, allowing customers to be billed based on usage. Direct current was compatible with electric motors, an advantage it held through the 1880s. However, the system's main limitation was its short transmission range—generators had to be placed in city centers, supplying customers within a mile to avoid expensive copper conductor costs.
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In 1884, George Westinghouse, an inventor and entrepreneur based in Pittsburgh, Pennsylvania, entered the electric lighting business by developing a direct current system and hiring William Stanley, Jr. to work on it. The following year, he came across an article in a UK technical journal called Engineering that described alternating current systems. By then, alternating current had gained a major advantage over direct current thanks to transformers that allowed voltage to be "stepped up" for long-distance transmission and then reduced for end users. This meant a central power station could supply electricity across areas up to seven miles wide. Westinghouse saw this as a chance to build a truly competitive system, rather than just another DC setup barely different enough to avoid Edison's patents. The limited range of Edison's DC plants also left gaps in coverage, which Westinghouse could easily fill with AC power.
In 1885, Westinghouse acquired the U.S. patent rights to a transformer designed by French engineer Lucien Gaulard, who had been funded by British engineer John Dixon Gibbs. The company brought several of these Gaulard–Gibbs transformers into the country, along with Siemens AC generators, to begin testing an alternating current system in Pittsburgh. That same year, William Stanley developed the first practical transformer using the Gaulard-Gibbs design and input from the Hungarian Ganz company’s Z.B.D. model. The Westinghouse Electric Company was established at the beginning of 1886.
In March 1886, Stanley, with Westinghouse's support, set up the first multi-voltage AC power system in Great Barrington, Massachusetts—a demonstration lighting system using incandescent bulbs. The setup could light twenty-three businesses along Main Street with minimal power loss over four thousand feet, using transformers to reduce 500 volts of AC current down to 100 volts for the lamps. By fall 1886, Westinghouse, Stanley, and Oliver B. Shallenberger had constructed the first commercial AC power system in the United States, located in Buffalo, New York.
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By the end of 1887, Westinghouse had 68 alternating current power stations, while Edison's company operated 121 DC-based stations. Things were getting worse for Edison because the Thomson-Houston Electric Company of Lynn, Massachusetts, which offered both AC and DC systems, had built 22 power stations. Thomson-Houston was expanding their business while trying to avoid patent conflicts with Westinghouse. They arranged deals like agreeing on lighting company territory, paying a royalty to use the Stanley AC transformer patent, and allowing Westinghouse to use their Sawyer-Man incandescent bulb patent. There were other competitors too, including the United States Illuminating Company and the Waterhouse Electric Light Company. All of these companies had their own electric power systems, arc lighting systems, and even incandescent lamp designs for domestic lighting, leading to constant lawsuits and patent battles between themselves and with Edison.
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Elihu Thomson of Thomson-Houston worried about the safety of alternating current and worked hard to create a lightning arrestor for high-tension lines, as well as a magnetic blowout switch to shut down the system during surges—a feature that was missing from the Westinghouse setup. He was also concerned about how customers would use the equipment after purchase, fearing they’d overload it with lights and generators in risky ways. Thomson thought using AC lighting in homes was too dangerous, so his company delayed those installations until a safer transformer could be built.
By the end of 1887, Manhattan's streets were a tangled mess of overhead wires—telephone, telegraph, fire and burglar alarm systems mixed with haphazardly strung AC lighting lines carrying up to 6,000 volts. In New York, where there was little regulation, these dangerous lines had become an eyesore and a hazard. Insulation was so poor one electrician said it was "as much value as a molasses covered rag," and weather wore it away over time. A third of the wires were abandoned by defunct companies, slowly deteriorating and causing short circuits in others. When a major snowstorm hit in March 1888, the Great Blizzard of 1888, many lines went down, cutting off utilities. The idea of moving them underground was proposed but blocked by a court injunction from Western Union. Legislation to force utilities to move their lines into city-supplied conduits was making progress, though the United States Illuminating Company argued their AC lines were safe.
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As AC systems spread into areas served by DC, companies began infringing on Edison's patents, including those for incandescent lighting. The rising cost of copper made Edison’s low-voltage DC system more expensive, since it needed heavier wires than higher-voltage AC systems. Even some of Edison’s own engineers urged him to consider AC, and his sales force kept losing bids to cheaper AC installations. Edward Hibberd Johnson, president of Edison Electric Illuminating Company, warned that sticking with all DC would prevent the company from serving small towns and mid-sized cities. Though Edison Electric held a patent option on the ZBD transformer, and electrical engineer Frank Sprague had recommended going AC in a confidential 1886 report, Thomas Edison remained opposed to the idea.
In a private letter written in November 1886 to Edward Johnson, Edison expressed his certainty that Westinghouse would cause a customer's death within six months of installing any sizable AC system. He believed the high voltage in AC systems posed too great a danger to be safe, and he thought it would take many years to make such technology reliable. For Edison, safety had been a key reason for designing his DC system, and he feared that a fatality from a faulty AC installation could damage public confidence in electricity overall. Though he understood how AC worked, Edison saw inefficiencies and high capital costs involved in large generating plants, leading him to doubt any financial benefits of AC ventures. He also felt that DC was inherently superior and suspected other companies were using AC merely to avoid his patents.
In February 1888, Edward Johnson, president of Edison Electric, released a detailed 84-page pamphlet called "A Warning from the Edison Electric Light Company." He sent it to newspapers and to businesses that had bought or were thinking about buying electrical equipment from Edison’s rivals, like Westinghouse and Thomson-Houston. The pamphlet claimed these companies were violating Edison’s patents and warned buyers they might lose in court if those patents were enforced. It promoted direct current as safer and more efficient, stating that DC had not caused a single death, while including reports of electrocution accidents involving alternating current.
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As arc lighting systems grew more common, reports emerged of people being killed by high voltage, often unsuspecting linemen struck down instantly. In 1881, a drunk dock worker died after touching a large electric dynamo in Buffalo, New York. That led dentist Alfred P. Southwick to work with physician George E. Fell and the Buffalo ASPCA, experimenting with electrocution on stray dogs. Their method, described in articles from 1882 and 1883, suggested using electricity as a replacement for hanging. Southwick’s idea used a device similar to a dental chair—a electric chair—and caught the attention of New York State politicians. After a series of failed hangings, Governor David B. Hill appointed a commission in 1886, which included Southwick. In 1888, that commission recommended executions be carried out by electricity using the electric chair.
When the death penalty commission began its work, it reached out to hundreds of experts in law and medicine, as well as electrical engineers such as Elihu Thomson and Thomas Edison. In late 1887, after contacting Edison, the commission member Southwick was told the inventor opposed capital punishment and wished no part in it. But under further pressure, Edison struck back at his rival George Westinghouse, suggesting that alternating machines made mostly in the U.S. by Westinghouse be used for executions. That December, he wrote to Southwick that such current would be best. Soon after the execution-by-electricity law was passed in June 1888, a New York official asked Edison how to carry out the new death sentence. His response was sharp and sarcastic: “Hire out your criminals as linemen to the New York electric lighting companies.”
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As deaths from high voltage lighting mounted across the country, a wave of tragedy in New York City in the spring of 1888 sparked a fierce public outcry against alternating current. On April 15, a 15-year-old boy was killed by a broken telegraph line energized with AC from the United States Illuminating Company. Two weeks later, a clerk died from an AC line. Then in May, a Brush Electric Company lineman was killed while cutting an AC line. The press turned sharply against AC and the dangerous overhead wires, shifting from debates about electric vs. gas lighting to stories of "death by wire," each incident deepening public fear and anger.
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At this point, Harold P. Brown, an electrical engineer who appeared unconnected to the Edison company, wrote to the editor of the New York Post on June 5, 1888. In his letter, he identified the alternating current (AC) system as the source of the issue. Brown declared the AC system was not only dangerous but “damnable,” and questioned why people should face the risk of sudden death merely to allow utility companies to rely on the less expensive AC setup.
In June 1888, after tensions rose between the two companies, Westinghouse tried to smooth things over. He wrote to Edison from Pittsburgh, inviting him to visit and saying, “I believe there has been a systemic attempt on the part of some people to do a great deal of mischief and create as great a difference as possible between the Edison Company and The Westinghouse Electric Co., when there ought to be an entirely different condition of affairs.” Edison thanked him for the offer but replied that “My laboratory work consumes the whole of my time.”
On June 8, Harold Brown showed up in person at the New York Board of Electrical Control. He asked that a letter he'd written to a newspaper be read into the meeting’s official record. He demanded strict limits on AC power, proposing a maximum voltage of three hundred volts, which would effectively kill AC's usefulness for long-distance power transmission. The board heard many challenges to Brown’s claims in letters and newspaper articles. Critics pointed out that Brown offered no scientific proof that AC posed more danger than DC. Westinghouse responded in newspaper letters, citing the number of fires caused by DC equipment. They suggested Brown was clearly under Edison's influence—a claim Brown always denied.
The Electrical Journal published an article in July that detailed Harold Brown's testimony before the New York Board of Electrical Control. The piece also reported on ongoing discussions among technical societies about whether direct current or alternating current was superior.
At a July meeting of the Board of Electrical Control, Harold Brown faced pushback over his criticisms of AC power. Some of the engineers challenging him worked for Westinghouse. Brown’s understanding of electricity itself was questioned. Supporters of AC shared stories from electricians who had survived shocks from as high as 1000 volts, arguing that DC posed a greater risk.
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Brown was determined to show that alternating current was more dangerous than direct current, so he reached out to Thomas Edison for help. Edison agreed immediately and offered Brown access to his equipment and laboratory space. Before long, Brown was given use of the West Orange, New Jersey lab, along with a laboratory assistant named Arthur Kennelly.
Brown used local kids to gather stray dogs for his experiments comparing direct and alternating current. After killing several dogs in early tests, he held a public demonstration on July 30 at Columbia College. A caged dog survived 1,000 volts of direct current but died instantly when exposed to 330 volts of alternating current. Four days later, he gave a second show, this time killing three dogs in quick succession with 300 volts of AC. Brown told a colleague he was confident this would convince the New York Board of Electrical Control to cap AC use at 300 volts. Though his push failed, similar legislation came close to passing in Ohio and Virginia.
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Francis S. Hastings, treasurer of Edison Electric Light, conceived the plan to enlist Brown and several New York doctors in attacking Westinghouse and other AC companies. He believed Westinghouse had acted unethically in securing lighting contracts in Denver and Minneapolis. Hastings arranged for Brown to meet with Edison and maintained regular contact with him. Edison Electric reportedly funded parts of Brown’s work highlighting the dangers of AC. Thomas Edison wrote personally to Scranton, Pennsylvania's authorities, praising Brown’s expertise on AC risks. Some of this cooperation came to light when letters from Brown’s office were stolen and released in August 1889.
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During this time, Westinghouse kept investing heavily in building a full AC system. In 1887, he bought Consolidated Electric Light to get the Sawyer-Man lamp patents. The next year, he purchased the Waterhouse Electric Light Company, and in 1890, the United States Illuminating Company. That gave him control over major incandescent lamp patents not already owned by Edison. In April 1888, Westinghouse engineer Oliver B. Shallenberger created an induction meter using a rotating magnetic field to measure AC usage. Then in July 1888, Westinghouse paid to license Nikola Tesla's U.S. patents for a poly-phase AC induction motor and also got a patent option on Galileo Ferraris’ design. Though this AC motor was key to completing their system, cash flow problems by 1890 slowed development. Funding was hard to come by, and that year J.P. Morgan first tried to take over Westinghouse Electric.
Thomson-Houston kept growing by snapping up seven smaller electric companies, including the Brush Electric Company in 1889. By 1890, the company controlled most of the arc lighting systems in the United States and had built up a collection of its own AC patents. But some deals between Thomson-Houston and Westinghouse fell through, and in April 1888 a judge ruled part of Westinghouse’s original Gaulard Gibbs patent only applied to transformers connected in series.
With help from financier Henry Villard, the Edison group of companies merged several smaller firms: the Edison Lamp Company in East Newark, New Jersey; Edison Machine Works in Schenectady, New York; Bergmann & Company, which made lighting fixtures and sockets; and Edison Electric Light Company, the patent-holding arm backed by J.P. Morgan and the Vanderbilt family. These companies came together to form Edison General Electric Company in January 1889, with Drexel, Morgan & Co. and Grosvenor Lowrey involved in the process and Villard named as president. The new company later added the Sprague Electric Railway & Motor Company to its portfolio.
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Through the fall of 1888, the battle between Edison and his allies continued to heat up, especially with Brown targeting Westinghouse directly. In November, George Westinghouse responded to Brown’s claim in the Electrical Engineer that Westinghouse's AC systems had caused thirty deaths. The magazine looked into the allegation and concluded that at most only two of those deaths could be linked to Westinghouse installations.
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Although New York’s criminal procedure code said that electrocution had to happen via an electric chair, it didn’t say what kind of electricity to use or how much current, since those details were still unknown back then. So the New York Medico-Legal Society, made up of doctors and lawyers, was asked to figure it out. Between late 1888 and early 1889, they ran a series of animal experiments to test voltage levels, electrode designs, and how skin conducts electricity. Harold Brown was brought in as a consultant during this time. The work ended up drawing the war of currents into the debate over capital punishment in the U.S.
In September 1888, the Medico-Legal Society created a committee to examine claims about alternating current. Frederick Peterson chaired the group and had previously worked at Columbia College where Brown conducted public electrocutions of dogs using AC in July 1888. Peterson brought the results of those experiments before the committee. Some members raised concerns about the scientific validity of the tests, noting that they used animals much smaller than humans. During their meeting in November, the committee advised setting the voltage at 3,000 volts but did not decide whether to use direct or alternating current.
In order to prove AC was more dangerous than DC, Brown contacted Francis S. Hastings, treasurer of Edison Electric Light, to use the West Orange laboratory. On December 5, 1888, Brown ran tests with animals larger than humans—four calves and a lame horse—all killed using 750 volts of alternating current. Members of the press, the Medico-Legal Society, and the chairman of the death penalty commission watched. Thomas Edison was also present. Based on these results, the Medico-Legal Society recommended using 1,000 to 1,500 volts of AC for executions. Newspapers noted this voltage was half what flowed through American city power lines.
Westinghouse called the tests a biased attack on alternating current, accusing Brown of working for Edison. In a letter to the New York Times on December 13, Westinghouse explained why Brown’s experiments were flawed and repeated his claim that Brown was Edison’s employee. Brown replied on December 18, denying those accusations and challenging Westinghouse to a kind of electrical duel. Brown said he would accept increasing doses of DC power if Westinghouse did the same with AC power, starting with the lower amounts and quitting if he lost. Westinghouse refused the challenge.
In March 1889, members of the Medico-Legal Society began a new set of tests to determine the best methods for electrode placement and composition. They asked Brown for technical help, and Edison’s treasurer Hastings tried without success to get a Westinghouse AC generator for the experiments. Because of that, they ended up using Edison’s laboratory in West Orange for the animal testing.
In March, Superintendent of Prisons Austin Lathrop asked Brown to supply the electrical equipment for executions and design the electric chair. Brown declined the chair design but agreed to provide the needed equipment. The state didn’t pay upfront, so Brown turned to Edison Electric and Thomson-Houston Electric Company for help. This led to a behind-the-scenes effort to get Westinghouse AC generators, reportedly with support from Edison and Thomson-Houston’s rival. Thomson-Houston swapped three Westinghouse generators for new ones. President Charles Coffin had two reasons: he didn’t want his equipment linked to the death penalty and wanted to prove Westinghouse’s claim of 50% greater efficiency was false by setting up a public test.
That spring Brown published "The Comparative Danger to Life of the Alternating and Continuous Electrical Current," a 61-page booklet detailing animal experiments done at Edison's lab. The report claimed AC was far deadlier than DC. It was professionally printed, possibly paid for by the Edison company.
In May 1889, when William Kemmler became the first person executed in New York's electric chair, the New York Times debated what to call this new method of execution. The paper considered terms like “Westinghoused,” “Gerrycide,” and “Browned.” The Times rejected “electrocution,” calling it pushed forward by “pretentious ignoramuses.” One of Edison’s lawyers wrote that while Edison preferred dynamort, ampermort, and electromort, he thought “Westinghoused” was the best option.
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William Kemmler faced execution in the electric chair in late June 1889, but just before the sentence was carried out, an appeal emerged. The appeal argued that using the electric chair violated the U.S. Constitution by constituting cruel and unusual punishment. The press and those involved quickly noticed that the lawyer who filed the appeal, William Bourke Cockran, had no real connection to the case. Instead, he was linked to the Westinghouse company, suggesting he was being paid for his efforts.
During fact-finding hearings that began on July 9 in New York City, Cockran cross-examined Brown, Edison, and their supporters with skill and force. He challenged Brown’s claims about AC's lethality and suggested Brown had falsified tests, possibly colluding with Edison, which Brown denied. Witnesses testified about electrical encounters, and medical experts discussed how electricity affects the human body. Brown was accused of using lower DC current in animal tests and hiding that fact. When the hearing moved to Edison’s West Orange lab for demonstrations, Brown clashed with a Westinghouse representative, accusing him of industrial espionage. Newspapers reported public doubt about the electrocution law, but after Edison testified, many accepted his assurance that 1,000 volts of AC would easily kill a man.
After all the evidence was presented and both sides had made their arguments, Judge Edwin Day ruled against Kemmler’s appeal on October 9, 1890. The case then moved to the U.S. Supreme Court, which refused to hear it on May 23, 1890. That decision effectively ended the legal challenge to the use of alternating current in electrical systems.
On August 6, 1890, William Kemmler became the first person executed by electric chair. The technicians misjudged the voltage, and after the first shock, Kemmler was still breathing. They had to try again, and a reporter described the second attempt as "an awful spectacle, far worse than hanging." George Westinghouse, who had been developing alternating current technology, later said: "They would have done better using an axe."
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"For Shame, Brown!" was the headline of a scandalous expose that revealed shocking details about an electric killing scheme. The article accused a state's expert of shady dealings, claiming he was paid by one electric company to harm a rival. The title itself—“Disgraceful Facts About the Electric Killing Scheme; Queer Work for a State's Expert; Paid by One Electric Company to Injure Another”—laid bare the corruption at the heart of the battle between AC and DC currents, exposing how far some would go to control the future of electricity.
The story came from 45 letters found in Brown’s office, revealing his secret deals with Thomson-Houston and Edison Electric. Most of the letters were between Brown and Thomson-Houston about buying three Westinghouse generators for New York, including one used in an efficiency test. Brown had also received $5,000 from Edison Electric to buy those surplus generators. Edison’s involvement showed up in letters from treasurer Hastings asking Brown to send anti-AC pamphlets to Missouri legislators—paid by the company. Brown also asked for a letter of recommendation from Thomas Edison to help him in Scranton, Pennsylvania. Edison and Arthur Kennelly were coaching Brown ahead of his testimony in the Kemmler appeal trial.
Brown didn’t back down after the revelation came to light. He went on to describe his attempts to expose Westinghouse as no different than targeting a grocer who sells poison but calls it sugar.
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In 1889, another wave of deaths linked to alternating current occurred, including a lineman in Buffalo, New York, four linemen in New York City, and a fruit merchant who died when his display touched an overhead line. NYC Mayor Hugh J. Grant, speaking with the Board of Electrical Control and AC companies, rejected claims that the lines were safe, saying “we get news of all who touch them through the coroners office.” On October 11, John Feeks, a Western Union lineman, was working on what he thought were low-voltage telegraph lines in Manhattan when he touched a high-voltage AC line that had been shorted many blocks away. The current entered his right hand and exited his left boot, killing him instantly. His body sparked and smoldered for nearly an hour while thousands watched below. The exact source of the power that killed him was never determined, though lines from the United States Illuminating Company were nearby.
After Feeks’ public death, fear spread among people living under electric lines, leading to what became known as the “Electric Wire Panic.” The blame fell heavily on Westinghouse, since the company had purchased many of the lighting firms involved, and people assumed Feeks’ death was their fault. Newspapers fueled the outcry, accusing AC companies of valuing profits over safety, with one headline calling for executives to be charged with manslaughter. The October 13, 1889, New Orleans Times-Picayune warned that “Death does not stop at the door, but comes right into the house.” Harold Brown’s reputation was quickly restored as reporters and magazines sought his opinion, following him through New York City where he measured how much current was leaking from AC power lines.
In November 1889, Edison entered the public debate over electricity for the first time, writing an article in the North American Review titled "The Dangers of Electric Lighting." He criticized the idea of burying high-voltage lines, calling it a flawed solution that would merely shift the danger underground and leave people’s homes and lives at risk. Edison claimed that AC current could not be made safe without reducing its voltage, and he declared that Edison Electric would never use AC as long as he was in charge.
George Westinghouse was painted as a villain defending unsafe pole-mounted AC power lines, and he stumbled through interviews, trying to deflect by pointing out other city dangers. But his response in the North American Review improved significantly. He noted that his AC system used lower household voltages than Edison’s DC setup. He also cited that 87 people died in one year from street cars and gas lighting, while only five accidental electrocutions were linked to AC current, and none had happened inside homes.
The crowd that watched Feeks included many New York aldermen, since the accident happened near government offices and the horror of it pushed them to act. They passed a law requiring utilities to be moved underground. The electric companies got an injunction to stop the lines from being cut right away, but they shut down most of their lighting until things were resolved, leaving many streets dark. The legislation was finally upheld by the New York Supreme Court in December. AC lines were cut, and for the rest of the winter, many streets stayed in darkness. Little had been done by the city supervisors from Tammany Hall, who were supposed to arrange for underground “subways” to house the wires.
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The war of currents was winding down, with direct current clearly losing out, even as Westinghouse’s propaganda efforts continued. Thomas Edison, who had fiercely opposed AC power, was stepping away from the electric power business. He had lost control of his company after the 1889 merger that created Edison General Electric. In 1890, he told president Henry Villard he was ready to leave the lighting industry behind and turned his attention to an iron ore refining project. His strong stance against AC no longer drove the company forward. By 1889, subsidiaries of Edison Electric were already pushing for AC transmission in their systems. Then, in October 1890, Edison Machine Works began developing equipment based on AC technology.
With Thomas Edison no longer involved, the war of currents ended in 1892 when Edison General Electric merged with Thomson-Houston. Henry Villard, who had orchestrated the original merger, pushed for a deal that would save both companies money and end patent disputes. But Edison opposed it, believing his company was strong enough to dictate terms. J.P. Morgan, however, saw Thomson-Houston as the stronger firm and engineered a behind-the-scenes agreement announced April 15, 1892, giving control of the new company, now called General Electric, to Thomson-Houston’s management. Edison wasn’t told until the day before it happened.
The war of currents ended when fifteen electric companies merged into just two: General Electric and Westinghouse. This happened after the Edison company, with its lighting patents, joined forces with Thomson-Houston, which held the AC patents. Together, they controlled three quarters of the U.S. electrical business. From that point on, both General Electric and Westinghouse promoted alternating current systems. Edison tried to seem confident, telling the media how his stock had increased in value, but privately he was bitter about handing over his company and patents to the competition.
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The fight over AC and DC had ended with a financial merger, but the technical divide lingered. Alternating current’s ability to move power across long distances was slowly merging with the need to connect to older systems—single-phase AC, poly-phase AC, low-voltage incandescent lighting, high-voltage arc lighting, and DC motors in factories and streetcars. To bridge the gap, engineers used rotary converters and motor-generators that allowed these different technologies to work together on the new AC grid. As time went on, these stopgap solutions were gradually replaced when older systems were retired or upgraded.
In May 1892, Westinghouse Electric won the contract to electrify the World's Columbian Exposition in Chicago by underbidding General Electric, even though they didn’t make a profit from the project. Their successful demonstration of a safe and flexible alternating current system at the fair helped them win the bid later that year to build an AC power station at Niagara Falls. Although General Electric was awarded contracts for AC transmission lines and transformers in that same project, they quickly caught up in the AC field thanks to Charles Proteus Steinmetz, a Prussian mathematician who first fully understood AC power mathematically. GE also hired many talented new engineers to improve their designs of transformers, generators, motors, and other electrical equipment.
In 1891, at the International Electro-Technical Exhibition in Europe, Mikhail Dolivo-Dobrovolsky showed how a three-phase three-wire system could send electricity over 176 kilometers with 75% efficiency. That same year, he also built the world’s first three-phase transformer and designed a short-circuited, or squirrel-cage, induction motor. He went on to create the first three-phase hydroelectric power plant, laying the groundwork for modern electrical systems.
Patent fights were still dragging both companies down and costing them money when J. P. Morgan stepped in to arrange a patent sharing deal in 1896. The agreement was between Edison's company and Westinghouse, and it lasted eleven years.
In 1897, Edison sold his remaining shares in Edison Electric Illuminating of New York to fund his iron ore refining project. Then, in 1908, he told George Stanley—son of William Stanley Jr., the inventor of the AC transformer—"Tell your father I was wrong." That remark likely admitted Edison had underestimated how much alternating current could develop.
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Some cities kept using DC power far into the 20th century. Central Helsinki maintained a DC network until the late 1940s, while Stockholm didn’t give up its last traces of DC electricity until the 1970s. Where DC systems were still in operation, mercury-arc valve rectifier stations helped convert AC to DC. In Boston, Massachusetts, sections of Beacon Street and Commonwealth Avenue continued to provide 110 volts of DC as late as the 1960s. This created issues for Boston University students who brought small appliances such as hair dryers and phonographs—ignoring warnings—only to have them destroyed by the incompatible current.
Consolidated Edison kept delivering direct current to New York City customers who had embraced it early in the century, particularly for elevators. The New Yorker Hotel, built in 1929, retained its DC power plant and didn’t fully switch to AC until the 1960s. That was where Nikola Tesla spent his last years and died in 1943. Broadway theaters also relied on DC service until 1975, using outdated manual dimmer boards operated by stagehands. The shift finally came when new technology allowed for computerized lighting control, ending the long use of DC on Broadway.
In January 1998, Consolidated Edison began phasing out direct-current service, which at the time served 4,600 customers. By 2006, that number had dropped to just 60 users. On November 14, 2007, the company shut down its final direct-current distribution system. Those remaining DC users were given on-site AC to DC rectifiers to keep their power flowing. Even later, in 2012, Pacific Gas and Electric Company still supplied DC power to certain areas of San Francisco—mostly for elevators—using nearly 200 rectifiers, each serving about seven to ten customers.
The Central Electricity Generating Board in the UK kept a 200-volt DC station running at Bankside Power Station in London until 1981. That station powered DC printing machines exclusively on Fleet Street, which was the center of the UK’s newspaper industry at the time. When the newspaper industry relocated to the emerging docklands area later that same year, 1981, and began using newer AC-powered equipment, the old DC system was shut down.
High-voltage direct current systems are still used today for moving large amounts of electricity from faraway power plants, especially when the lines have to go underwater. They’re also used to connect separate alternating-current networks. These uses show how direct current continues to play a role in modern energy transmission, even as alternating current dominates most electrical grids.
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