Missouri has had four Constitutions starting from 1820 and ending with the fourth and final Constitution in 1945. Missouri was recognized as a state on August 10, 1821 and was created from the Louisiana Territory that the United States government purchased in 1803 from the French leader Napoleon.
The first constitution took quite some time to approve because the state was attempting to enter the union as a slave state. At this time, in the early 1800s, there were pro-slave states and anti-slave states. With the addition of Missouri, there would have been more pro-slave states in the United States and this would have upset the political balance. However, the government was able to come to an agreement when Maine was accepted as an anti-slave state and the balance was maintained.
The second and third constitutions were created in order to update the constitution with new laws. The second occurred near the end of the Civil War and the third was created to allow Supreme Court justices to be elected and to limit taxation in the state. The final and fourth constitution was simply to bring voters into a new modern era with a "Bill of Rights" created specifically for Missouri citizens as well as more detailed laws regarding the executive branch powers in the state legislature.