1889: North Dakota and South Dakota were admitted to the Union as the 39th and 40th states, respectively. The first European to reach the region was Pierre Gaultier de Varennes, sieur de La Vérendrye, a French-Canadian fur trader and explorer who, in 1738, led an expedition to what is present-day North Dakota. In 1742 and 1743, two of his sons, Louis-Joseph and François de La Vérendrye, returned to the territory and ultimately reached present-day Fort Pierre, in the center of South Dakota, where they buried a lead plate as a marker for their mission. At that time, at least eight Native American tribes populated the vicinity including the Mandan, Arikara, Hidatsa, Assiniboin, Crow, Cheyenne, Cree, and the Dakota (Santee Sioux). Other than through fur trapping, exploration of the Dakotas by European Americans was practically nonexistent prior to the 1803 Louisiana Purchase. In 1804, the Lewis and Clark expedition wintered in present-day North Dakota. (Source: Library of Congress)