thumb|The river and the [[Theodore Roosevelt National Park appear with Roosevelt on the reverse of the 2016 America the Beautiful quarter.]]

The Little Missouri River is a tributary of the Missouri River, long, in the northern Great Plains of the United States. Rising in northeastern Wyoming, in western Crook County about west of Devils Tower, it flows northeastward, across a corner of southeastern Montana, and into South Dakota. In South Dakota, it flows northward through the Badlands into North Dakota, crossing the Little Missouri National Grassland and all three units of Theodore Roosevelt National Park. In the north unit of the park, it turns eastward and flows into the Missouri in Dunn County at Lake Sakakawea, where it forms an arm of the reservoir long called Little Missouri Bay and joins the main channel of the Missouri about northeast of Killdeer.

The highly seasonal runoff from badlands and other treeless landscapes along the Little Missouri carries heavy loads of eroded sediment downstream. The sedimentary layers, which extend from the headwaters in Wyoming all the way to the mouth in North Dakota, vary in age, but most of the beds along the river belong to the Bullion Creek and Sentinel Butte formations, both deposited during the Paleocene (about 66 to 56 million years ago).

See also

  • List of rivers of North Dakota
  • List of longest rivers of the United States (by main stem)
  • List of rivers of Montana
  • List of rivers of South Dakota
  • List of rivers of Wyoming
  • Montana Stream Access Law

References

  • Wyoming State River Plan: Little Missouri River
  • The Lewis and Clark Trail: The Little Missouri River
  • National Park Service: North Dakota Segments
  • 2016 Theodore Roosevelt National Park Quarter image (depicting the Little Missouri River)