Fort Peck Dam was originally designed in the early 1930s without hydroelectric power production. After the dam was completed, powerhouses were added to help meet the nation's growing demand for electricity. Water from Fort Peck Lake is diverted to the powerhouses to create hydroelectric power, and when the water hits the turbine, the pressure forces it to spin like a giant waterwheel. Construction began on powerhouse #1 in 1941 and was completed in 1951, and it first generated power in 1943. Powerhouse #2 was completed in 1961. Together, the powerhouses produce approximately one billion kilowatt hours of electricity each year, helping provide power to approximately 400,000 people in Montana.