The Birthplace of the AC Grid

Folsom Powerhouse was the first to transmit power over long distance

3 min read

Joanna Goodrich is the associate editor of The Institute

A brick building attached to electric transformers across the road from it

The Folsom Powerhouse in California, was the first facility to send high-voltage alternating current over long-distance transmission lines. It brought electricity to Sacramento over a 35-kilometer-long distribution line using newly invented AC generators and hydroelectric power.

Wirestock, Inc./Alamy

Back in the 1800s, electricity distribution was a short-range business, driven by nearby DC generators. That changed in 1895. On 13 July of that year, the Folsom Powerhouse, in California, became the first facility to send high-voltage alternating current over long-distance transmission lines. It brought electricity to Sacramento over a 35-kilometer-long distribution line using newly invented AC generators and hydroelectric power. The facility generated three-phase 60 Hz AC electricity—the standard in the United States today—and powered Sacramento businesses such as Buffalo Brewing, as well as the California State Capitol building and the city's streetcars.

On the 126th anniversary of the achievement, 13 July, the Folsom Powerhouse was commemorated with an IEEE Milestone. The IEEE Sacramento Valley Section sponsored the nomination. You can watch the dedication ceremony on the facility'sFacebook page.

Administered by the IEEE History Center and supported by donors, the Milestone program recognizes outstanding technical developments around the world.


Horatio Gates Livermore moved from Maine to California in 1850 during the Gold Rush in pursuit of riches, according to a walking tour of Folsom and the facility, which is now a state historic park. After 12 years of mining gold, however, Livermore became more interested in building a logging business and sawmill. He sought to use water wheels powered by the 48-km-long American River to operate sawmills and other industrial plants in the Folsom area. The river runs from the Sierra Nevada mountains to downtown Sacramento, where it connects to the Sacramento River.

In 1862, he and his sons, Horatio Putnam and Charles Edward, bought Natoma Water and Mining, in Sacramento, to turn the dream into reality. The company owned a network of dams, ditches, and reservoirs that supplied water to the numerous gold mines located around the American River, according to the facility's website.

In the mid-1860s, the company started construction on a dam in the town of Folsom to provide a pond that would store the logs cut in the higher foothills before they were sent down the river to the sawmill.

The company faced several challenges, however, including finding affordable labor—which delayed construction for many years. After Livermore died in 1892, his sons were able to complete the project by hiring inmates at the San Quentin prison.

The brothers saw a business opportunity larger than just generating power for the sawmills. Instead, they set their sights on providing power to Sacramento with the help of a new technology: hydroelectric power. Folsom is 37 km from Sacramento.


Although the two brothers didn't build the first electric power plant in the world, it was the largest one at the time and the first to use AC generators.

Photo of a blue electric generator The 750-kilowatt, 2.6 meters tall AC generators that were used at Folsom Powerhouse were manufactured by General Electric in Schenectady, N.Y.Everett Collection Historical/Alamy

The Folsom Powerhouse's main building contained four 750-kilowatt generators that were each 2.6 meters tall and weighed more than 25 metric tons. The generators—manufactured by General Electric in Schenectady, N.Y.—were the "largest three-phase dynamos yet constructed," according to an 1895 report in The Electrical Journal. A 2,896-meter-long canal parallel to the American River, completed in 1893, provided water power to the generators through four dual turbines invented by John B. McCormick. Each pair of generators produced 1,260 horsepower. The turbines were powered by river water that flowed through four 2.4-meter penstocks—channels to regulate the flow that had gates that could be closed to turn off the water.

The generators' voltage output was increased from 800 volts to 11,000 by recently invented Stanley transformers. The high voltage allowed the electricity to be sent on a system developed by Louis Bell, chief engineer of the power transmission department at GE. If the AC generators failed, the facility had two small DC generators as backups.

Horatio, Charles, and Albert Gallatin, a partner in Huntington, Hopkins Hardware, formed the Folsom Water Power Co. It supplied water to Sacramento Electric Power and Light, which the three men founded in 1892.

On 13 July 1895, with two generators in operation, electricity was successfully transmitted over 35 km of uninsulated copper wire to Sacramento.

The facility was acquired in 1902 by California Gas and Electric, headquartered in San Francisco, and three years later became part of Pacific Gas and Electric.

The Folsom Powerhouse provided electricity to Sacramento for nearly five decades. In 1952 PG&E donated the powerhouse to California, according to an article about the facility on PG&E's blog. The original Folsom dam was removed to make way for a larger dam, and the facility was designated a state historic park.

The Milestone plaque is to be displayed at the Folsom Powerhouse State Historic Park. The plaque reads:

Folsom was one of the earliest electrical plants to generate three-phase alternating current, and the first using three-phase 60 hertz. On 13 July 1895, General Electric generators began transmitting electricity 22 miles to Sacramento at 11,000 volts, powering businesses, streetcars, and California's capitol. The plant demonstrated advantages of three-phase, 60 hertz long-distance transmission, which became standard, and promoted nationwide development of affordable hydropower.

The Conversation (18)
Scott Hayes
Scott Hayes23 Dec, 2021

The Folsom Powerhouse and the IEEE Milestone Plaque does not claim it to be the first electrical generator, AC generator or 3 phase generator. It claims to be the first 3 phase 60 Hz generator and transmitted 3 phase power that was sold to multiple businesses. The first 3 Phase generator in the US is generally considered to be Mill Creek Hydro generator that is located in Southern California near the town of Redlands. It was operated at 50 Hz until after World War II making Folsom Powerhouse the first 3 phase 60 Hz generator in the US..

John Macdonald
John Macdonald24 Dec, 2021

I appreciated Joanna Goodrich’s article about the Folsom Powerhouse and IEEE Milestone dedication ceremony.  Folsom was indeed a great milestone in the commercialization of AC power distribution.  However, in 1895, it was not the first 3-phase system, nor was it the first to transmit power long distance.

AC power distribution was first demonstrated experimentally at Great Barrington, MA in 1886, 9 years before Folsom.  This system, pioneered by William Stanley, sent 500 V single-phase AC at 133-1/3 Hz a distance of 1.2 km.  That same year, the first commercial AC system was turned on in Buffalo, NY.  Built by Westinghouse and Stanley, it transmitted 1000 V single-phase about 2 km.

The first polyphase demonstration was the Lauffen-to-Frankfurt (175 km) system, pioneered by Dobrovolsky.  It was built for the 1891 International Electro-Technical Exposition, and it generated 180 kW of 3-phase AC at 20 kV and 40 Hz.  It was by far the longest transmission distance to date, although it was only experimental.

The first commercial polyphase system was the Redlands, CA Powerhouse.  Built by General Electric and pioneered by Elihu Thomson and William Stanley, this was the first 3-phase system.  It began operation in 1893, generating 250 kW at 50 Hz, and transmitted over 11 km.

The Folsom Powerhouse, which began operation in 1895, was notable (as your article points out) for its size and the fact that it operated at 60 Hz (a relatively unimportant distinguishment).  It was also engineered by Thomson and Stanley of Redlands fame.  It developed 3000 kW at 11 kV and sent it 36 km.  Note that this is not the first 3-phase system, nor the longest distance to date.  But it was the highest power to date.

Still, all of these are dwarfed by the Niagara Falls Adams Power Station, built by Westinghouse and Tesla, using many of Stanley’s patents.  This project had been underway since about 1890.  The scope and size of it meant that it was still being built during the turn-on of many of the above-mentioned smaller systems.  It was first tested in April, 1895 (before Folsom), and began commercial operation in 1896. This system is most notable because it generated an amazing 35 MW of power (35 times the power level of Folsom).  Initially it distributed 40 km to Buffalo using 2-phase, 25 Hz at 11 kV.

When discussing the history of electricity, it is hard not to conclude that Niagara Falls was truly the first implementation of widespread and commercially-viable power distribution.

John Macdonald
John Macdonald24 Dec, 2021

Well, to be clear, I'm just trying to set the record straight. I have tremendous respect for the work that went into the Folsom Powerplant, and the article that Goodrich published. With all respect to Goodrich, I just wanted to point out that the article has a few statements which, for posterity to all of us and our followers, should be corrected. For example:

- The subhead of the article, and why it immediately caught my attention, is, "...the first to transmit power over long distance". This is demonstrably false. (see my earlier post).

- In the article, it says that Folsom was the first to send high-voltage AC. This is also not true (see my earlier post).

- The article says that Folsom was the 1st to use 60 Hz. As far as I can tell, this is true but irrelevant. Europe uses 50 Hz; US uses 60 Hz. It's not that important. There's an engineering trade between "not so fast that the generators can't keep up" and "not so slow that the human eye can see the flicker". It turns out, that's around 40-100 Hz. We have settled on a 60 Hz standard.

- The article correctly states that Folsom was not the 1st electric power plant in the world.

- The article correctly states that Folsom was the largest power plant put into operation at that date.

- The article incorrectly states that Folsom was the 1st to use AC generators. (see my earlier post).