Why did Missouri want to join the union?
because its a free country
The Missouri Compromise of 1820 allowed Missouri to join the Union as a slave-state. At the outbreak of the Civil War in 1861, Lincoln allowed Missouri to continue practising slavery for the duration of hostilities, so as not to drive it into the arms of the Confederacy. The 13th Amendment (December 1865) outlawed slavery in every state of the Union.