A steady increase in population and impending statehood were among the factors driving the addition of new counties to Missouri in 1818-1821.
The original districts of St. Charles, St. Louis, Ste. Genevieve, Cape Girardeau, and New Madrid were designated as counties in 1812. In 1815, the territorial legislature designated a strip of southern Missouri and part of northern Arkansas as a new Lawrence County, Missouri, and Washington County formed from Ste. Genevieve County. Settlement up the Missouri River drove the formation of Howard County in 1816.
The designation of new counties began in earnest in 1818, when the territorial legislature designated 10 more counties, including Madison and Wayne in southeastern Missouri. Ten more were formed in 1820, including Perry in southeast Missouri.
At the time of statehood, New Madrid County encompassed an area between the St. Francis River and the Mississippi, north to Byrds Point. Cape Girardeau (including present-day Bollinger) extended north to Apple Creek and west to Castor River, with Madison and Wayne west of there. Wayne extended to the western boundary of the state and north of Lawrence county—so large it was sometimes referred to as the “State of Wayne.” Perry had roughly its present boundaries, as did Ste. Genevieve County. Washington County went from Big River and Ste. Genevieve/Madison to the western boundary of the state.
Three other counties were of exceptional size in 1821: Ralls included much of the northeast one-third of the state, Ray was bounded by a long stretch of the Missouri River, and Lillard (now Lafayette) extended from the Osage River to the Missouri River in a large area on the west side of the state. In all, Missouri had 26 counties by statehood, eventually to be joined by 88 more to become today’s 114.