river rising in two headstreams in the Blackfeet Indian Reservation in the Rocky Mountain foothills, northwestern Montana, U.S. Both streams flow northeastward into Alberta, Can., where they unite as the Milk River, which, after flowing east for about 100 miles (160 km), bends southeastward to reenter Montana. The river then flows in an easterly direction across the state to enter the Missouri River below Nashua, a few miles northeast of the Fort Peck Dam and Reservoir (1940), after a course of 625 miles (1,006 km). Near Havre, Mont., much of the river's water, stored in a lake created by Fresno Dam (1939), is used for irrigation.