Formed October 1, 1812 (3rd county)
Saint Charles County (405,262), Saint Charles (70,539), O’Fallon (91,347)
The old stone courthouse was erected in 1901 and replaced in 1993 with a Modern red brick facility. It is augmented by a 1988 Justice Center and a 1994 Administration Center. The new facility is on 2nd Street and Jefferson. Missouri Highway 94 passes 4 blocks to the north of the courthouse. Sverdrup CRSS are the new courthouse architects. There was also an 1846 courthouse. The old courthouse served as one of the capitols for Missouri. It has a small rotunda and a lot of marble features inside. Saint Charles County was founded on October 1, 1812 as an original county (3rd county) with Saint Charles as the only county seat. The county and county seat are named for Cardinal and later saint Charles Borromeo.
Saint Charles County government consists of a sheriff, an administrator, an attorney, a collector, a coroner, an assessor and a clerk (executive). It has 7 Council Members (legislative.) Six Circuit Court Judges, Seven County Court Judges and a court clerk serve Saint Charles County (judicial.) The county is on the eastern border with Illinois. The Missouri River forms its southern border. Saint Louis, Missouri is directly southeast of the county. The county center is 8.3 miles West of Saint Charles in Saint Peters. The county is surrounded clockwise by Illinois and Saint Louis, Franklin, Warren, and Lincoln counties.
The area of the county is 561 square miles. It is 65 out of 115 in the state. It ranks 3 out of 115 in population in the state. It has a density of 722.4 persons per square mile making it 4 out of 115 in the state. Saint Charles County has 76.7% of its population in its incorporated areas. Interstate Highway 70 travels east to west through the county from Saint Louis County to Warren County. United States Highway 40 enters from the southeast, Saint Louis County, and joins Interstate Highway 70 to exit into Warren County. United States Highway 61 is joined with United States Highway 40 from Saint Louis County, splits, and goes north into Lincoln County. United States Highway 67 clips the northeast tip of the county from Illinois, north, to Saint Louis County, south. The county resembles the head of a crane. The City of Saint Charles is located in the northern third of the county. O’Fallon is in the western third of the county. Saint Charles is the county seat and O’Fallon is the largest city. Saint Charles is 17.4% of the county population while O’Fallon is 22.5% of the county population. This county is in the Saint Louis Metropolitan Statistical Area.
Augusta
Cottleville
Dardenne Prairie
Flint Hill
Josephville
Lake St Louis
New Melle
O’Fallon
Portage Des Sioux
St Charles
St Paul
St Peters
Weldon Spring
Weldon Spring Heights
Wentzville
West Alton
Foristell