The Great Falls of the Missouri River are a series of waterfalls on the upper Missouri River in north-central Montana in the United States. From upstream to downstream, the five falls along a segment of the riverCutright, Paul Russell, and Johnsgard, Paul A. Lewis and Clark: Pioneering Naturalists. 2d ed. Lincoln, Neb.: University of Nebraska Press, 2003. are: Black Eagle Falls () Colter Falls () Rainbow Falls () Crooked Falls, also known as Horseshoe Falls () Big Falls, also known as the Great Falls, ()

The Missouri River drops a total of from the first of the falls to the last, which includes a combined of vertical plunges and of riverbed descent."Great Falls of the Missouri River." Encyclopedia Americana. New York: Americana Corp., 1954. The Great Falls have been described as "spectacular",Malone, Michael P. Montana Century: 100 Years in Pictures and Words. Guilford, Conn.: Globe Pequot, 1999. one of the "scenic wonders of America",Montana Department of Agriculture. The Resources and Opportunities of Montana. Helena, Mont.: Montana Department of Agriculture, 1912. and "a major geographic discovery".Johnsgard, Paul A. Lewis and Clark on the Great Plains: A Natural History. Lincoln, Neb.: University of Nebraska Press, 2003. When the Lewis and Clark Expedition became the first white men to see the falls in 1805, Meriwether Lewis said they were the grandest sight he had beheld thus far in the journey.Pritchett, Michael. The Melancholy Fate of Capt. Lewis. Columbia, Mo.: Unbridled Books, 2007.

The Great Falls of the Missouri River were depicted on the territorial seal of the Montana Territory, and later on the state seal of Montana in 1893.Shearer, Barbara Smith. State Names, Seals, Flags, and Symbols: A Historical Guide. 3rd rev. ed. Santa Barbara, Calif.: Greenwood Publishing Group, 2002.

Names of the falls The Mandan Indians knew of cataracts and called them by a descriptive (but not formal) name: Minni-Soze-Tanka-Kun-Ya,McEneaney, Terry. The Birder's Guide to Montana. Guilford, Conn.: Falcon Press, 1993. or "the great falls."Robbins, Chuck. Great Places: Montana: A Recreational Guide to Montana's Public Lands and Historic Places for Birding, Hiking, Photography, Fishing, Hunting, and Camping. Belgrade, Mont.: Wilderness Adventures Press, 2008. The South Piegan Blackfeet, however, had a formal name for Rainbow Falls and called it "Napa's Snarling."Federal Writers' Project. Montana: A State Guide Book. Washington, D.C.: Federal Works Agency, Work Projects Administration, 1939. Napa or "Old Man" (spelling variants include Naapi, Napi, Nape, Napiw, and Napioa) is a benevolent trickster spirit in the Blackfoot religion. Napa is also depicted as foolish or a troublemaker. The Creator gave him the task of shaping the world, and he continues to help people, according to various Blackfoot legends. See Clark, Cora and Williams, Texa Bowen. Pomo Indian Myths and Some of Their Sacred Meanings. New York: Vantage Press, 1954; Linderman, Frank Bird. Indian "Why Stories": Sparks From War Eagle's Lodge-Fire. New York: C. Scribner's Sons, 1915; Plenty-Coups and Linderman, Frank Bird. Plenty-Coups, Chief of the Crows. Reprinted. Lincoln, Neb.: University of Nebraska Press, 2002. (orig. pub. 1930) No record exists of a Native American name for any of the other four waterfalls.

Four of the five waterfalls were given names in 1805 by American explorers Meriwether Lewis and William Clark.Judson, Katharine Berry. Montana: "The Land of Shining Mountains". 5th ed. Chicago: A.C. McClurg, 1909. Both Lewis and Clark named Crooked Falls in their journals. Clark named three of the remaining waterfalls on his map: "Great Falls" (which retains its name to this day),Lewis and Clark had been told by the Mandan Indians that there were "great falls" on the Missouri River. Clark adopted this name for the largest set of waterfalls the expedition discovered. See: Howard, Lewis & ClarkExploration of Central Montana, 2000. "Beautiful Cascade" (now called Rainbow Falls), and "Upper Pitch" (now known as Black Eagle Falls).Howard, Ela Mae. Lewis & ClarkExploration of Central Montana. Rev. ed. Guilford, Conn.: Globe Pequot, 2000. "Beautiful Cascade" was renamed "Rainbow Falls" in 1872 by Thomas B. Rogers, an engineer with the Great Northern Railway. Colter Falls received its name from Paris Gibson, in honor of John Colter (a member of the Lewis and Clark Expedition). Black Eagle Falls is named for the black eagle which built a nest in a cottonwood tree on an island in the middle of the falls.Vaughn, Robert. Then and Now, or, Thirty-Six Years in the Rockies: Personal Reminiscences of Some of the First Pioneers of the State of Montana, Indians and Indian Wars, and the Past and Present of the Rocky Mountain Country: 1864–1900. Chicago: Tribune Printing Company, 1900. It is not clear when the falls lost their original name of "Upper Pitch," but they had acquired their modern name by at least 1877.Strahorn, Carrie Adell. Fifteen Thousand Miles By Stage: A Woman's Unique Experience During Thirty Years of Path Finding and Pioneering From the Missouri to the Pacific and From Alaska to Mexico. New York: G. P. Putnam's Sons, 1911.

Geological history

The Missouri River lies atop the Great Falls Tectonic Zone, an intracontinental shear zone between two geologic provinces of basement rock of the Archean period which form part of the North American continent, the Hearne province and Wyoming province.Boerner, D. E.; Craven, J. A.; Kurtz, R. D.; Ross, G. M.; and Jones, F. W. "The Great Falls Tectonic Zone: Suture or Intracontinental Shear Zone?" Canadian Journal of Earth Sciences. 35:2 (1998); O'Neill, J. Michael and Lo, David A. "Character and Regional Significance of Great Falls Tectonic Zone, East-Central Idaho, and West-Central Montana." AAPG Bulletin. 69 (1985); Mueller, Paul A.; Heatherington, Ann L.; Kelly, Dawn M.; Wooden, Joseph L.; and Mogk, David W. "Paleoproterozoic Crust Within the Great Falls Tectonic Zone: Implications for the Assembly of Southern Laurentia." Geology. 30:2 (February 2002); Harms, Tekla A.; Brady, John B.; Burger, H. Robert; and Cheney, John T. "Advances in the Geology of the Tobacco Root Mountains, Montana, and Their Implications for the History of the Northern Wyoming Province." Precambrian geology of the Tobacco Root Mountains, Montana. Special Papers, Volume 377. John B. Brady, H. Robert Burger, John T. Cheney, and Tekla A. Harms, eds. Boulder, Colo.: Geological Society of America, 2004. Approximately 1.5 million years ago, the Missouri River, Yellowstone River and Musselshell River all flowed northward into a terminal lake.Clawson, Roger and Shandera, Katherine A. Billings: The City and the People. Helena, Mont.: Farcountry Press, 1998. McRae, W.C. and Jewell, Judy. Moon Montana. 7th ed. Cambridge, Mass.: PublicAffairs, 2009. During the last glacial period, the Laurentide and Cordilleran ice sheets pushed these lakes and rivers southward.Montagne J.L. "Quaternary System, Wisconsin Glaciation." Geologic Atlas of the Rocky Mountain Region. Denver: Rocky Mountain Association of Geologists, 1972. Between 15,000 and 11,000 BCE, the Laurentide Ice Sheet blocked the Missouri River and created Glacial Lake Great Falls.Hill, Christopher L., and Valppu, Seppo H. "Geomorphic Relationships and Paleoenvironmental Context of Glaciers, Fluvial Deposits, and Glacial Lake Great Falls, Montana." Current Research in the Pleistocene. 14 (1997); Hill, Christopher L. "Pleistocene Lakes Along the Southwest Margin of the Laurentide Ice Sheet." Current Research in the Pleistocene. 17 (2000); Hill, Christopher L., and Feathers, James K. "Glacial Lake Great Falls and the Late-Wisconsin-Episode Laurentide Ice Margin." Current Research in the Pleistocene. 19 (2002); Reynolds, Mitchell W. and Brandt, Theodore R. Geologic Map of the Canyon Ferry Dam 30' x 60' Quadrangle, West-Central Montana: U.S. Geological Survey Scientific Investigations Map 2860, scale 1:100,000. Scientific Investigations Map 2860. Washington, D.C.: U.S. Geologic Survey, 2005."Luminescence Dating of Glacial Lake Great Falls, Montana, U.S.A." Feathers, James K., and Hill, Christopher L. XVI International Quaternary Association Congress. Stratigraphy and Geochronology Session. International Quaternary Association, Reno, 2003. About 13,000 BCE, as the glacier retreated, Glacial Lake Great Falls emptied catastrophically in a glacial lake outburst flood. The current course of the Missouri River essentially marks the southern boundary of the Laurentide Ice Sheet."Agriculture." In Encyclopedia of the Great Plains. David J. Wishart, ed. Lincoln, Neb.: University of Nebraska Press, 2004. The Missouri, Yellowstone and Musselshell rivers flowed eastward around the glacial mass, eventually settling into their present courses. As the ice retreated, meltwater poured through the Highwood Mountains and eroded the mile-long, Shonkin Sag—one of the most famous prehistoric meltwater channels in the world.Axline, Jon, and Bradshaw, Glenda Clay. Montana's Historical Highway Markers. Rev. ed. Helena, Mont.: Montana Historical Society, 2008. ; Bowman, Isaiah. "Forest Physiography: Physiography of the United States and Principles of Soils in Relation to Forestry." American Environmental Studies. Reprint ed. Charles Gregg, ed. New York: Arno Press, 1970.

The Great Falls themselves formed on a fall line unconformity in the Great Falls Tectonic Zone.Botkin, Daniel B. Beyond the Stony Mountains: Nature in the American West from Lewis and Clark to Today. New York: Oxford University Press, 2004. The Missouri River settled into a bedrock canyon which lay beneath the clay laid down by Glacial Lake Great Falls.Fisher, Cassius A. "Geology of the Great Falls Coal Field, Montana." Bulletin - United States Geological Survey. Issue 356. Washington, D.C.: U.S. Geological Survey, 1909.Newberry, J. S. "Surface Geology of the Country Bordering the Northern Pacific Railroad." American Journal of Science. July–December 1885. The course of the Missouri in and around the Great Falls has changed very little since then, in comparison to lower regions of the river on the ground moraine that forms much of the upper Great Plains.Maschner, Herbert D. G., and Chippindale, Christopher. Handbook of Archaeological Methods. Vol. 1. New York: Rowman Altamira, 2005.

The Great Falls of the Missouri River formed because the Missouri is flowing over and through the Kootenai Formation, a mostly nonmarine sandstone laid down by rivers, glaciers, and lakes in the past.DeCelles, Peter G. "Sedimentation in a Tectonically Partitioned, Nonmarine Foreland Basin: The Lower Cretaceous Kootenai Formation, Southwestern Montana." Geological Society of America Bulletin. 97:8 (August 1986). Some of the Kootenai Formation is marine, however, laid down by shallow seas.Haney, M. and Schwartz, R. K. Estuarine Member of the Lower Cretaceous Kootenai Formation, Missouri River Gorge, Great Falls, MT. Paper No. 38-15. Northeastern Section, 38th Annual Meeting. Geological Society of America. March 27–29, 2003; Farshori, M. Zahoor, and Hopkins, John C. "Sedimentology and Petroleum Geology of Fluvial and Shoreline Deposits of the Lower Cretaceous Sunburst Sandstone Member, Mannville Group, Southern Alberta." Bulletin of Canadian Petroleum Geology. 37:4 (December 1989). The river is eating away at the softer nonmarine sandstone, with the harder rock forming the falls themselves. Until relatively recently (in geologic time) the Missouri River in the area had a much wider channel,Geologic Map of the Great Falls North 30' x 60' Quadrangle, Central Montana. Vuke, Susan M.; Colton, Roger B.; and Fullerton, David S. Montana Bureau of Mines and Geology Open File 459. Helena, Mont.: Montana Bureau of Mines and Geology, 2002. but it has now settled into its current course, where it will continue to cut more deeply into the sandstone.

Discovery Early inhabitants