The Mandan, Hidatsa, and Arikara Nation (MHA Nation), also known as the Three Affiliated Tribes ( Mandan: Miiti Naamni; Hidatsa: Awadi Aguraawi; Arikara: ačitaanu' taWIt), is a Native American Nation resulting from the alliance of the Mandan, Hidatsa, and Arikara peoples, whose native lands ranged across the Missouri River basin extending from present day North Dakota Through western Montana and Wyoming.
After the signing of the Fort Laramie Treaty and subsequent taking of land, the Nation's land base is currently approximately 1 million acres located Fort Berthold Reservation in northwestern North Dakota. The Tribe reported a total enrollment of 16,085 registered tribe members in July 2018.   Nearly 5,200 live on the reservation; others live and work elsewhere.
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Membership (Citizenship) is derived from the 1936 Indian Census roll of the Three Affiliated Tribes. In 2010 the tribal membership passed amendments specifying " blood quantum," or minimum amounts of tribal ancestry to qualify individuals for membership and for candidates for public office. Effective December 16, 2010 individuals must have at least 1/8 Mandan, Hidatsa, or Arikara ancestry (the equivalent of one full-blooded great-grandparent) to become an enrolled member of the MHA Nation and 1/4 ancestry to serve in elected office. 
The Tribal Business Council consists of six Segment Representatives and a Chairman. Each member's term lasts 4 years, and there are no term limits. The Tribal Business Council holds Regular Meetings on the second Thursday of each month, and sub-committees meet at different times throughout the month. A legal quorum as defined in the constitution of the Three Affiliated Tribes is 5 of the 7 council representatives. 
|Chairman||Mark Fox||MHA Nation||2018|
|Treasurer||Mervin Packineau||Parshall/Lucky Mound||2018|
|Executive Secretary||Fred Fox||White Shield||2016|
|Member||Judy Brugh||Four Bears||2018|
|Member||Cory Spotted Bear||Twin Buttes||2018|
|Member||Dr. Monica Mayer||New Town/Little Shell||2016|
The Mandan, who refer to themselves as Nueta, are a Native American tribe currently part of the Three Affiliated Tribes of North Dakota. At the height of their historic culture, the Mandan were prosperous and peaceful farmers and traders, noted for their excellent maize cultivation and crafting of Knife River flint. They built earth lodges, and made villages of considerable technical skill, and cultivated many varieties of maize. They were a more sedentary people than other, more nomadic tribes of the Great Plains.
Lewis and Clark stayed with the Mandan when they passed through the Upper Missouri region on their expedition to the Northwest, including five months in the winter of 1804-1805. Sakakawea, a Hidatsa who has subsequently been claimed by both the Shoshone and Hidatsa, joined the expedition as an interpreter and native guide. Because of her role in salvaging the expedition, she was honored with an image on the U.S. dollar coin. On the return trip, the expedition brought the Mandan chief Sheheke Shote with them back to Washington, DC.
The smallpox epidemic of 1837–1838 decimated the Mandan, leaving approximately 125 survivors and severely impacting their society. They banded together with the Hidatsa to survive. Later, when the Arikara were forced northward by wars with the Lakota, they also settled with the Hidatsa and Mandan forming a confederacy that would later be known as the Three Affiliated Tribes. The Nation now commonly uses the Mandan, Hidatsa and Arikara Nation in most situations although The Three Affiliated Tribes of the Fort Berthold Indian Reservation is used as well.
When European-American settlers began arriving in this territory in number in the late 19th century, the US relocated the three tribes to the Fort Berthold Reservation in 1870. Under the Indian Reorganization Act of 1934, the tribes formed a tribal government which they called the Three Affiliated Tribes, a sovereign Tribal Nation. Today over 15,000 tribal members live throughout the United States and internationally, however the population is concentrated on the reservation and nearby cities in North Dakota.
Some explorers described the Mandan and their structures as having "European" features. In the 19th century, a few people used such anecdotes to speculate that the Mandan were, in part, descended from lost European settlers who had arrived at North America before 1492, the voyage of Christopher Columbus. One legend associated them with having Welsh ancestry. Historians and anthropologists have debated this history, however, the MHA people and their oral tradition agree that there was historic admixture. This is the legend of Madoc ab Owein, popularized in relation to the Mandan in the 19th century by the painter George Catlin. The current center of Mandan culture and population is the community of Twin Buttes, North Dakota.
The Hidatsa, called Moennitarri by their allies the Mandan, are a Siouan-speaking people. The Hidatsa name for themselves ( autonym) is Nuxbaaga ("Original People"). The name Hidatsa said to mean "willows," was that of one band's village, after a prominent landscape feature. When the villages consolidated, the tribe used that name for their people as a whole.
Their language is related to that of the Crow nation. They have been considered a parent tribe to the modern Crow in Montana. The Hidatsa have sometimes been confused with the Gros Ventre, another tribe which was historically in Montana. In 1936, the Bureau of Indian Affairs compiled the Tribe's Base Roll listing all Hidatsa as "G.V.", for Gros Ventre. Today about 30 full-blood Hidatsa are members of the Affiliated Three Tribes. Most Hidatsa people have ancestry also of the Mandan and Arikara tribes.
The Arikara call themselves Sahnish.  The Arikara were forced into Mandan territory by conflict with the Lakota (Sioux), between the Arikara War and the European-American settlement in the 1870s. The Arikara lived for many years near the Fort Clark trading post, also called Knife River.
In 1862 they joined the Hidatsa and Mandan at Like-a-Fishhook Village, near the Fort Berthold trading post. For work, the Arikara men scouted for the U. S. Army, stationed at nearby Fort Stevenson. In 1874, the Arikara scouts guided Custer on the Black Hills Expedition, during which his party discovered gold. This resulted in a rush of miners to the area, causing conflict with the Lakota, who considered the Black Hills to be sacred.
In 1876, a large group of Arikara men accompanied Custer and the 7th Cavalry on the Little Big Horn Expedition. Arikara scouts were in the lead when US Army forces attacked the widespread encampment of thousands of Sioux and Cheyenne warriors and families. Several scouts drove off Lakota horses, as they had been ordered, and others fought alongside the troopers. Three Arikara men were killed: Little Brave, Bobtail Bull, and Bloody Knife. During the subsequent confusion, when the scouts were cut off from the troopers, they returned to the base camp as they had been directed. After the battle, in which Custer and some 260 other US troops were killed, the search for scapegoats resulted in some critics mistakenly accusing the scouts of having abandoned the soldiers.
- Ruth Buffalo, elected to the North Dakota House of Representatives in 2018
- Edward Lone Fight (b. 1940), former Chairman of the Three Affiliated Tribes
- Tex G. Hall, Chairman of the Three Affiliated Tribes from 1998 to 2006
- Denise Juneau, State Superintendent of Public Instruction for Montana
- Destrey Zarfos, Disc Jockey for 93X
Minneapolis-St. Paul rock radio station
- Lisa Lone Fight, Remote Sensing and Environmental Scientist
- "Demographics | North Dakota Studies". ndstudies.gov. Retrieved August 1, 2016.
- Sevant, Taft (July 13, 2018). "Three Affiliated Tribes Mandan, Hidatsa, and Arikara Nation Office of Tribal Enrollment" (PDF). mhanation.com. Retrieved July 23, 2018.
- "MHA Nation Tribal Enrollment FAQ". mhanation.com. MHA Nation. 2012. Retrieved 13 January 2015.
- "Elected Officials". mhanation.com. MHA Nation. 2014. Retrieved 13 January 2015.
- "History: The Sahnish (Arikara)." Archived 9 November 2011 at the Wayback Machine Mandan, Hidatsa, and Arikara Nation. Retrieved 29 September 2011.
- Gilman, Carolyn, Mary Lane Schneider, et al. The Way to Independence: Memories of a Hidatsa Indian Family, 1840-1920. St Paul: Minnesota Historical Society Press, 1987. ISBN 0-87351-209-X.
- Libby, Orin G., ed. Arikara Narrative of Custer's Campaign and the Battle of the Little Bighorn, Norman: University of Oklahoma Press, 1998. ISBN 0-8061-3072-5.
- Hammer, Ken. With Custer in '76, Norman: University of Oklahoma, 1976.
- Matthews, Washington. Ethnography and Philology of the Hidatsa Indians, U.S. Geological and Geographical Survey, 1877.
- Nichols, Ron. Men with Custer, revised ed. Hardin, MT: Custer Battlefield Historical and Museum Association, 2000.
- Wilson, Gilbert Livingstone, Ph.D. Agriculture of the Hidatsa Indians: an Indian Interpretation, University of Minnesota, 1917.