Named for one of the Native American groups that once lived in the territory, Missouri became a U.S. possession as part of the Louisiana Purchase of 1803. In 1817, Missouri Territory applied for statehood, but the question of whether it would be slave or free delayed approval by Congress. In 1820, the Missouri Compromise was reached, admitting Missouri as a slave state but excluding slavery from the other Louisiana Purchase lands north of Missouri's southern border. Missouri's August 1821 entrance into the Union as a slave state was met with disapproval by many of its citizens.
In 1861, when other slave states seceded from the Union, Missouri chose to remain; although a provincial government was established in the next year by Confederate sympathizers. During the war, Missourians were split in their allegiances, supplying both Union and Confederate forces with troops. Lawlessness persisted during this period, and Missouri-born Confederate guerrillas such as Jesse James continued this lawlessness after the South's defeat. With the ratification of Missouri's new constitution by the citizens of the state in 1875, the old divisions were finally put to rest.