Grand River National Grassland is in northwestern South Dakota, USA. It is named for the Grand River. The North and South forks of the river meet in the grassland. It has a land area of 154,783 acres. In descending order of acreage it lies in parts of Perkins, Corson, and Ziebach counties. The portion in Corson County also lies within the Standing Rock Indian Reservation. The portion in Ziebach County also lies within the Cheyenne River Indian Reservation.

https://www.fs.usda.gov/recarea/dpg/recarea/?recid=79472