Milk River (Missouri tributary)

Water type: River
Continent: North America
Climates: Arid (desert), Continental

Milk River is a tributary of the Missouri River, 729 miles (1,173 km) long, in the U.S. state of Montana and the Canadian province of Alberta.

Rising in the Rocky Mountains, the river drains a sparsely populated, semi-arid watershed of 23,800 square miles (62,000 km2), ending just east of Fort Peck, Montana.

It is formed in Glacier County in northwestern Montana, 21 miles (34 km) north of Browning, Montana, by the confluence of its South and Middle forks. The 30-mile (48 km) long South Fork and 20-mile (32 km) long Middle Fork both rise in the Rocky Mountains just east of Glacier National Park, in the Blackfeet Indian Reservation. Much of the water in the North Fork is diverted from the St. Mary River through a canal and inverted siphon.