Folsom Powerhouse State Historic Park, Historic hydroelectric power station in Folsom, United States.

Folsom Powerhouse State Historic Park preserves an 1895 hydroelectric station on the American River in Folsom, California. Its two-story brick and granite powerhouse, with a stepped parapet and round-arched windows, holds four water turbines and AC generators, two of which were running when power first reached Sacramento. The Tennessee marble-faced control switchboard and original machinery remain in place.

This power station opened in 1895 during California's rapid industrial growth and need for reliable electricity sources. It became a testing ground for new electrical technologies, particularly alternating current systems that would soon transform power generation worldwide.

The powerhouse's four three-phase generators, driven by Francis turbines, produced three megawatts at 800 volts, stepped up to 11,000 volts for the line to Sacramento. The Tennessee marble-faced control switchboard and the original generators remain in place, and docent-guided tours by California State Parks explain how the plant worked.

The park sits along the riverbank and is easily accessible by car with free parking available on-site. Wear comfortable shoes since exploring both powerhouses and the grounds involves considerable walking through the historic buildings and outdoor areas.

The electricity produced here was transmitted to distant cities using methods that were revolutionary for the time. This successful demonstration of long-distance power transmission proved the technology could work at scale and changed how energy systems would be built elsewhere.