• River: Missouri River
• Surface Area: 245,000 Acres
• Shoreline: 1,520 Miles
• Length: 134 Miles
• Volume: 18,700,000 Acre Feet
• Drainage Area: 10,200 Square Miles
• Average Depth: 76 Feet
• Maximum Depth: 220 feet
Fort Peck Lake, or Lake Fort Peck, is a major reservoir in Montana, formed by the Fort Peck Dam on the Missouri River. The lake lies in the eastern prairie region of Montana approximately 140 miles east of Great Falls and 120 miles north of Billings, reaching into portions of six counties.
The dam and reservoir were built in response to severe flooding along the Missouri River in the early 20th century, which hampered the economic development of the Missouri River Valley and damaged production of military supplies for then-ongoing World War II. In response, the federal government created the Pick-Sloan Plan, calling for a series of dams and reservoirs to be built along the Missouri and its tributaries. Fort Peck Dam was built from 1933 to 1940 by the U.S. Army Corps of Engineers; water impoundment began in 1937 and the reservoir was first filled to capacity in 1947.
With a volume of 18,700,000 acre feet when full, Fort Peck is the fifth largest artificial lake in the United States. It extends 134 miles through central Montana, and its twisting, inlet-studded shoreline has a total length of some 1,520 miles. Along with the Missouri River, smaller tributaries such as the Musselshell River, Fourchette Creek, Timber Creek, Hell Creek and Dry Creek feed the reservoir; the latter forms the longest side arm of the reservoir, which reaches some 30 miles southwards. The lake covers an area of 245,000 acres, making it the largest in Montana by surface area, although Flathead Lake has a larger volume due to its greater depth.
The reservoir is also a tourist attraction, with 27 designated recreational sites bordering its shores. Bordering nearly the entire reservoir is the 1,719-square-mile. Charles M. Russell National Wildlife Refuge, which has preserved much of the high prairie and hill country around the lake in a more or less natural state.