SUN RIVER

river, northwest-central Montana, U.S. It rises in the Flathead National Forest, in Teton county near the Continental Divide, and flows south and east into the Missouri River at Great Falls, after a course of 130 miles (209 km). The Sun River irrigation project includes a system of dams and reservoirs on branches of the main stream. The reservoirs include Greenfield Lake, Pishkun, and Freezeout Lake. Gibson Dam on the North Fork Sun is one of the largest in the project.