Thief River Falls, also called Thief River or TRF, is a city in Pennington County, Minnesota, United States. It is the county seat of Pennington County. It is located at the confluence of the Red Lake River and the Thief River. U.S. Route 59 and Minnesota State Highways 1 and 32 are the three main arterial routes in the city. Thief River Falls is located approximately 70 miles south from the Canadian border, and 50 miles northeast from Grand Forks, North Dakota, in the Northwest region of Minnesota.