Milk River (Alberta–Montana)
The Milk River in Writing-on-Stone Provincial Park
|Name origin: Named by the Lewis and Clark Expedition for its milky color|
|Countries||United States, Canada|
|Source||Confluence of South and Middle Forks|
|- location||Glacier County, Montana|
|- elevation||4,403 ft (1,342 m)|
|- location||Valley County, Montana|
|- elevation||2,024 ft (617 m)|
|Length||729 mi (1,173 km)|
|Basin||23,800 sq mi (61,642 km2) |
|Discharge||for Nashua, Montana, 22.7 mi (36.5 km) from the mouth|
|- average||618 cu ft/s (17 m3/s) |
|- max||45,300 cu ft/s (1,283 m3/s)|
|- min||0 cu ft/s (0 m3/s)|
The Milk River (Assiniboine: Asą́bi wakpá, Wakpá jukʾána ) is a tributary of the Missouri River, 729 mi (1,173 km) long, in the United States 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 sq mi (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.
The main stream flows east-northeast into southern Alberta, where it is joined by the North Fork of the Milk River, then east along the north side of the Sweetgrass Hills. It flows past the town of Milk River and Writing-on-Stone Provincial Park, then turns southeast into Montana, passing through the Fresno Dam, then east past Havre and along the north side of the Fort Belknap Indian Reservation. Near Malta, it turns north, then southeast, flowing past Glasgow and joining the Missouri in Valley County, Montana, 5 miles (8.0 km) downstream from Fort Peck Dam.
The Milk is the northernmost major tributary of the Missouri, and thus represents the rough northern extent of the Mississippi watershed. The small area drained by the Milk River in southern Alberta and southwestern Saskatchewan is one of two areas in Canada that drain into the Gulf of Mexico (The others are the Big Muddy Creek and Poplar River watersheds which extend into Canada in Saskatchewan.)
- "the water of this river possesses a peculiar whiteness, being about the colour of a cup of tea with the admixture of a tablespoonfull of milk. from the colour of its water we called it Milk river."
This appearance results from clays and silts suspended in its waters. These extremely fine-grained sediments are the result of the erosion of soft clay-rich rocks along the Milk River basin in southern Alberta.
At the time of Lewis's exploration, the Milk River drainage was legally part of the United States as a component of the Louisiana Purchase. However, in 1818 U.S. negotiators swapped a portion of the Milk River watershed that lay north of 49° north latitude, receiving in exchange a parcel of Red River of the North drainage that had previously been part of British North America.
See also 
- Montana Stream Access Law
- List of longest rivers of Canada
- List of longest rivers of the United States (by main stem)
- List of rivers of Montana
- List of rivers of Alberta
- "Milk River". Geographic Names Information System, U.S. Geological Survey. 1980-04-04. Retrieved 2011-10-28.
- "Overview of the Milk River Watershed". Milk River Watershed Council Canada.
- "USGS Gage #06174500 on the Milk River at Nashua, MT". National Water Information System. U.S. Geological Survey. 1939-present. Retrieved 2011-10-28.
- "AISRI Dictionary Database Search--prototype version. Assiniboine. "Montana"". Retrieved 2012-05-26.
- ACME Mapper. Topo Maps for United States and Canada (Map). Cartography by United States Geological Survey and Natural Resources Canada. http://mapper.acme.com/. Retrieved 2011-10-28.
- "Milk River Project". U.S. Bureau of Reclamation. 2011-05-11. Retrieved 2011-10-28.