When did Missouri become a U.S state?

Answer 1

Missouri was admitted as a slave state on August 10, 1821, after an agreement known as the Missouri Compromise in which Maine was admitted as a free state.

In 1818, Missouri applied for statehood, but this was delayed because it was a Southern state that allowed slavery. By 1820, the controversy became a national issue as the issue of slavery was debated. The "Missouri Compromise" allowed Missouri to enter the Union as a slave state and Maine as a free state, thus keeping the balance of slave and free states equal in Congress. Although Missouri was allowed to enter as a slave state, the remaining portion of the Louisiana Purchase area, north of the 36° 30' line, was to be forever free of slavery.

When the Civil War broke out, the Missouri legislature voted to secede and join the Confederacy. However by that time, the Union had taken control of the State capital. So Missouri officially remained a Union state.

Answer 2

Missouri was admitted into the Union on August 10, 1821 becoming the 24th state to join the Union.