North Dakota is a state located in the Midwestern and Western regions of the United States of America. The 19th largest state by area in the U.S., it is the 48th most populous, with just over 640,000 residents as of 2006. North Dakota was carved out of the northern half of the Dakota Territory and admitted to the Union as the 39th state on November 2, 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 contains lignite coal and oil. In the east, the Red River forms the Red River Valley, holding fertile farmland. Agriculture has long dominated the economy and culture of North Dakota. The state capital is Bismarck and the largest city in the state is Fargo. The primary public universities are located in Grand Forks and Fargo. The United States Air Force operates bases at both Minot and Grand Forks.