Mandan is a city on the eastern border of Morton County and is the eighth-largest city in North Dakota. Founded in 1879 on the west side of the upper Missouri River, it was designated in 1881 as the county seat of Morton County. The U.S. Census Bureau estimated the 2016 population at 21,769. Located across the Missouri River from the state capital of Bismarck, Mandan is a core city of the Bismarck-Mandan Metropolitan Statistical Area.The city was named after the historic indigenous Mandan of the area. The Mandan are part of the Three Affiliated Tribes of the Fort Berthold Reservation, spanning the upper Missouri River in the western part of the state. Their people also live in cities of the state and other areas. In the 2010 census, nearly 5% of the people in the city of Mandan identified as Native American. In 2013, Mandan was selected a finalist in the Rand McNally "Most Patriotic City" competition.