In 1818, Missouri requested admittance to the Union as a slave state. This became a national controversy due to the delicate balance between free and slave states. In 1820, the Missouri Compromise cleared the way for Missouri's entry to the union as a slave state, along with Maine, a free state, to preserve the balance. Additionally, the Missouri Compromise stated that the remaining portion of the Louisiana Territory above the 36°30′ line was to be free from slavery. This same year, the first Missouri constitution was adopted. The following year, Missouri was admitted as the 24th state, with the state capital temporarily located in Saint Charles until a permanent location could be selected. Jefferson City was chosen in 1826 as the site for the capital.
Immediately before the Civil War began, Missourians voted overwhelmingly against seceding from the Union. However, in the 1860 presidential election, the Republican (and therefore anti-slavery) Abraham Lincoln received only a small percentage of Missouri votes, mostly from St. Louis. Northern Democrat Stephen A. Douglas won the state's 12 electoral votes — the only state he captured in his campaign. Sympathies ran for both sides, the Confederacy and the Union, and it was in Saint Louis where the first blood was spilled in the "Camp Jackson Massacre." Because of the mixed sympathies, Missouri was the only state in the Union that did not officially secede, but where the Army declared a state of war.
Secessionists formed their own unrecognized government seceded from the Union, joining the Confederacy and establishing a capital at Marshall, Texas. By the end of the war, Missouri had supplied 110,000 troops for the Union Army and 40,000 troops for the Confederate Army. In 1861, General John C. Fremont issued a proclamation that freed slaves owned by those that had taken up arms against the Union.
Because of the state's strategic location linking Northern and Southern states, many important Civil War battles occurred in Missouri. The state was the location of the largest number of engagements of any state.
In 1865, Missouri became the first slave state to abolish slavery, doing so before the adoption of the Thirteenth Amendment to the United States Constitution by an ordinance of immediate emancipation. Missouri adopted a new constitution, one that denied voting rights and had prohibitions against certain occupations for former Confederacy supporters.
Source: Wikipedia, the free encyclopedia