Timeline of Missouri History: 1820-1829
| 1820 | The Missouri statehood 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 | |
| 1820 | Missouri’s Enabling Act was passed and approved by President James Monroe (Mar. 6) |  Governor Alexander McNair |
| 1820 | Missouri’s first Constitution was adopted (Jul. 19) | |
| 1820 | Missouri’s first state elections were held and Alexander McNair was elected Missouri’s first governor (Aug. 28) | |
| 1820 | Missouri's first General Assembly began its first session at the Missouri Hotel in St. Louis (Sept. 18) | |
| 1821 | President James Monroe admitted Missouri as the 24th state; the state capitol was located in St. Charles until a permanent location was designated (Aug. 10) | |
| 1821 | The Santa Fe Trail was opened by William Becknell’s successful trading expeditions to Santa Fe (Sept. 1) | |
| 1821 | Governor Alexander McNair signed the bill designating the site for the City of Jefferson (Dec. 31) | |
| 1822 | A bill to create the Missouri State Seal was adopted (Jan. 11) | |
| 1825 | William Beaumont began research observing the human digestive system (Aug. 1) | |
| 1826 | Jefferson City was designated Missouri’s permanent seat of government; all state records, equipment, and the Great Seal were moved to Jefferson City on October 1st | |
| 1829 | Missouri State Library established by law (Jan. 22) | |