Missouri, a state near the geographical center of the United States, has three distinct physiographic divisions:
- a north-western upland plain or prairie region part of the Interior Plains' Central Lowland (areas Osage Plain 12f and Dissected Till Plains 12e) known as the northern plains
- a lowland in the extreme southeast bootheel region of Missouri, part of the Atlantic Plain known as the Mississippi Alluvial Plain (areas 3e) or the Mississippi embayment
- the Missouri portion of the Ozark Plateau (areas 14a and 14b) which lies between the Mississippi Alluvial Plain and the Central lowland.
The boundary between the northern plains and the Ozark region follows the Missouri River from its mouth at St. Louis to Columbia. This also corresponds to the southernmost extent of glaciation during the Pre-Illinoian Stage which destroyed the remnant plateau to the north but left the ancient landforms to the south unaltered. The Ozark boundary runs southwestward from there towards Joplin at the southeast corner of Kansas. The boundary between the Ozark and lowland regions runs southwest from Cape Girardeau on the Mississippi River to the Arkansas border just southwest of Poplar Bluff. Missouri borders eight other US States, more than any other state except Tennessee, which also borders eight states.