Folsom preserves an 1895 hydroelectric power station on the American River that became a turning point in electrical history. Unlike earlier low-voltage direct-current steam plants that served only nearby areas, this system used water power to generate alternating current, stepped up from 800 to 11,000 volts, and transmitted it 22 miles to Sacramento. When service began on July 13, 1895, it proved hydroelectric power could be generated away from a city and delivered economically over long distances using three-phase 60-cycle current. Its dam, canal, turbines, generators, and original control equipment together mark a major step in modern electrical transmission.