Hydropower production at Fort Peck Dam in Montana was approved by the Fort Peck Power Act in 1938. Started in 1941, construction on the first power house was not completed until 1951 due to shortages of supplies and materials during World War II. A second power house was later added to tunnel #2. Construction on it began in 1958 and was completed in 1961. Today the two power houses average 1.1 billion kilowatt hours a year, or enough power to supply a town of 100,000 people.