The Birthplace of the AC Grid

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 226th 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’s Facebook 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.

via IEEE Spectrum

Categories: Energy