Crook County is in the northeast corner of Wyoming with Montana to the north and South Dakota to the east. This is the home of Devils Tower National Monument and Keyhole State Park.

Named for Brigadier General George Crook (a famous US Army commander during the Indian Wars), Crook County was formally organized in 1875 and contains 2,859 square miles of land and 12 square miles of water. The county seat is Sundance.