North Dakota is a Midwestern state in the United States. It is the northernmost of the Great Plains states and is the northern half of The Dakotas. During the 19th century, North Dakota was considered part of the Wild West. Formerly part of Dakota Territory (named after the Dakota tribe of Native Americans), North Dakota became the 39th state in 1889. The Missouri River flows through the western part of the state and forms Lake Sakakawea behind the Garrison Dam. The western half of the state is hilly and is home to natural resources including lignite coal and crude oil. In the east, the Red River of the North forms the Red River Valley. This region has rich farmland. Agriculture has long dominated the economy and culture of North Dakota. The state capital is Bismarck. The largest city in the state is Fargo. Large public universities are located at Grand Forks and Fargo. The United States Air Force operates bases at both Minot and Grand Forks.