Marking the centennial of Missouri's admission to the Union as the 24th state in 1821, the Missouri commemorative half dollar. Two types were made, including one with the inscription 2*4, a scarcer variety proclaiming Missouri's place as the 24th state. The other type does not have this numerical feature and are referred to simply as plain Missouri halves.

Many of each type were made, but not all were sold, and a large number were melted. However, numismatic experts cannot find consensus on exactly how many were sold, though the total number of survivors is low, and both types of Missouri half dollars are very scarce. The Missouri half dollar was designed by Robert Aitken and were issued at $1 each.

About a third of known surviving specimens exhibit wear, and most Missouri half dollars are encountered in the range of AU50 to MS64. Availability drops off significantly at the MS65 level, where these pieces are quite rare. In MS66 or above they are very rare.