Upper Missouri




Text modified from Abell et al. 2000. Freshwater Ecoregions of North America: A Conservation Assessment. Island Press, Washington, DC, USA. Additional text provided by Jennifer Hales.


United States

Major Habitat Type

Temperate upland rivers

Drainages flowing into

The Missouri River is the largest tributary of the Mississippi River. The Missouri originates in the Rocky Mountains at the confluence of the Gallatin, Jefferson and Madison rivers. This ecoregion drains the basins of the Upper Missouri (Robison 1986).

Main rivers to other water bodies

Other rivers include the Yellowstone in Montana, the Bighorn River in Wyoming, the Little Missouri in all four states, the Grand River, the Moreau River, and the Cheyenne River in South Dakota.



This large ecoregion covers all of Montana east of the continental divide, most of northern Wyoming, the northwestern corner of Nebraska, western South Dakota, southwestern North Dakota, and a small portion of extreme southeastern Alberta and southern Saskatchewan. The ecoregion is largely defined by the watershed of the Upper Missouri River.


Rising over 4000 m at its headwaters in the Rockies, the Missouri River passes through mountainous caverns in the Rockies as well as flatter relief of the Great Plains (Robison 1986).

Freshwater habitats

This ecoregion represents the uppermost drainages of the Mississippi Basin, the largest watershed on the North American continent. The headwaters of this drainage are on the arid eastern slope of the Rocky Mountains. The land gradually slopes downward to the east. The streams change from high gradient mountain streams to slower moving, larger rivers on the plains. A distinctive feature of this ecoregion (along with ecoregions [148] and [143], and [109]) is the presence of isolated wetlands called prairie potholes. These wetlands, which are highly endangered, may harbor endemic species of aquatic invertebrates and plants.

Terrestrial habitats

Most of the ecoregion is characterized by grasslands of the Northern Great Plains, with dominant vegetation including grama (Bouteloua spp.), needlegrass (Stipa spp.) and wheatgrass (Agropyron spp.). Western edges of the ecoregion are characterized by temperate coniferous forest dominated by Engleman spruce (Picea englemannii), subalpine fir (Abies lasiocarpa), and Douglas fir (Psuedotsuga menziesii) (Ricketts et al. 1999).

Description of endemic fishes

The Upper Missourihas no known endemic fish, mussel, crayfish, or aquatic herpetofauna species.

Justification for delineation

Ecoregion boundaries are taken from Abell et al. (2000) and are based on subregions defined by Maxwell et al. (1995).


  • Ricketts, T. H.,E. Dinerstein,D.M Olson;C.J. Loucks (1999). "Terrestrial ecoregions of North America: A conservation assessment" Washington, D.C.: World Wildlife Fund.
  • Robison, H. W. (1986). "Zoogeographic implications of the Mississippi River Basin" C. H. Hocutt and E. O. Wiley (Ed.) The zoogeography of North American freshwater fishes ( pp. 267-285 ) New York, New York, USA: Wiley.
  • Abell, R.,Olson, D.,Dinerstein, E.,Hurley, P. T.,Diggs, J. T.,Eichbaum, W.,Walters, S.,Wettengel, W.,Allnutt, T.,Loucks, C. J.;Hedao, P. (2000). "Freshwater ecoregions of North America" Washington, D.C.: Island Press.
  • Maxwell, J. R., Edwards, C. J., Jensen, M. E., et al. (1995) \A hierarchical framework of aquatic ecological units in North America (Nearctic Zone)\ St. Paul, MN. North Central Forest Experiment Station, USDA Forest Service.
  • Cross, F. B., R.L. Mayden and J.D. Stewart (1986). "Fishes in the western Mississippi drainage" C. H. Hocutt and E.O. Wiley (Ed.) The zoogeography of North American freshwater fishes ( pp. 363-412 ) New York, NY: John Wiley & Sons.