With the opening of the Black Hills to white settlement in the mid-1870s, thousands of fortune-seekers made their way into Dakota Territory. George Edward Lemmon, a man later renowned as one of the world's most accomplished cowboys, was among them. During the 1880s his employer, the Sheidley Cattle Company, grazed thousands of cattle in western Dakota Territory, many of them on Sioux Indian land. Indeed, the company owed a great deal of its success to illegal grazing on the Great Sioux Reservation. Opportunists such as Lemmon supported Indian reservations because they could use those lands to make a profit. The interaction between large-scale white ranchers and the Indians of the Great Sioux Reservation provides insight into the development of the range cattle industry in the northern Great Plains and illuminates the motivations that led many ranchers to support, rather than oppose, the reservation system.