23-Star Flag (1820)

1819 marked the beginning of open disagreement between the North and South over slavery.  Alabama was admitted into the Union on December 14, 1819, becoming the 11th slave state and matching the 11 free states in number.  Then Maine began pushing for statehood which, if granted, would upset the then existing balance between the two.  In an effort to pacify both sides over the slave issue, Sen. Jesse Thomas (IL) made a proposal that became known as the Missouri Compromise.  It provided that, with the exception of Missouri, no new slave states would be added from any lands obtained from the Louisiana Purchase north of the southern boundary of the Missouri Territory.  This compromise kept a tenuous peace between the North and South for a short while.

Congress voted to accept Maine as a free state and Missouri as a slave state, but due to problems with Missouri's constitution, only Maine was admitted into the Union in time for the next flag.  On March 15, 1820, Maine became the 23rd state and on July 4th of that year the official flag of the nation became the 23-star flag.