Thief River Falls, also called Thief River or TRF, is a city in Pennington County, Minnesota, United States. The population was 8,410 at the 2000 census. It is the county seat of Pennington County. U.S. Route 59 and Minnesota State Highways 1 and 32 are three of the main arterial routes in the city. The town is the home of snowmobile manufacturer Arctic Cat. South of Thief River Falls is one of the area's few Native American casinos, 7 Clans Casino, which also contains a hotel and indoor water park. Thief River Falls is home to the electronic parts distributor Digi-Key, one of the largest employers in the area, and was the birthplace of the vaunted Steiger Tractor, produced from 1958 to the late 1980s.