Missouri: Polity Style: 1820-2025

6 Mar 1820	the inhabitants of southeastern portion of the Territory of Missouri are authorized to form a constitution for further admission to the Union in accordance with an act passed by the Congress of the United States (House of Representatives on 1 Mar 1820, Senate on 2 Mar 1820 with amendments, the amendments are concurred in by the House on 2 Mar 1820), signed into law on 6 Mar 1820 (Statutes at Large, 3:545-548) [1]
19 Jul 1820	the Constitution of the State of Missouri is adopted by the Convention on 17 Jul 1820, signed by the members of the Convention on 19 Jul 1820 and came into operation on 18 Sep 1820 (Missouri Convention 1820, p. 46) [2]
18 Sep 1820 -	State of Missouri
2 Mar 1821	the admission of Missouri to the Union is agreed, depending on the fulfillment of a certain condition by the legislature of the State of Missouri, in accordance with a resolution of the Congress of the United States (passed by the House of Representatives on 26 Feb 1821, Senate on 28 Feb 1821), approved by the President of the United States on 2 Mar 1821 (Statutes at Large, 3:645) [3]
10 Aug 1821	the admission of the State of Missouri to the United States is declared to be complete in accordance with a proclamation of the President of the United States of 10 Aug 1821 (Statutes at Large, 3:797)

Full title: An Act to authorize the people of the Missouri territory to form a constitution and state government, and for the admission of such state into the Union on an equal footing with the original states, and to prohibit slavery in certain territories.
The Constitution did not include a clause fixing the date when it would come into operation, but Section 1 of the Schedule declared that "all writs, actions, prosecutions, judgments, claims, and contracts, of individuals, and of bodies corporate, shall continue as if no change had taken place; and all process which may, before the third Monday in September next, be issued under the authority of the Territory of Missouri, shall be as valid as if issued in the name of the state." The General Assembly of the State of Missouri met on 18 Sep 1820 and Alexander McNair was sworn in as the Governor of the State on 19 Sep 1820 before the Constitution was approved by the Congress of the United States.
Full title: Resolution providing for the admission of the state of Missouri into the Union on a certain condition.