The Nemaha Half-Breed Reservation was established by the Fourth Treaty of Prairie du Chien of 1830, which set aside a tract of land for the mixed-ancestry descendants of French-Canadian trappers and women of the Oto, Iowa, and Omaha, as well as the Yankton and Santee Sioux tribes. The Underground Railroad, a route staffed by volunteers' helping slaves escaped to the North, ran through the Reservation toward John Brown's Cave. This was its last stop, located 35 miles (56 km) north of the Tract.