St. Charles County, Missouri

St. Charles County
County
St. Charles County Courthouse in St. Charles
Flag
Location within the U.S. state of Missouri
Missouri's location within the U.S.
Coordinates: 38°45′36″N 90°37′00″W / 38.76°N 90.6167°W / 38.76; -90.6167
Country	United States
State	Missouri
Founded	October 1, 1812
Named for	Charles Borromeo
Seat	St. Charles
Largest city	O'Fallon
Government
• County executive	Steve Ehlmann (R)
Area
• Total	593 sq mi (1,540 km2)
• Land	560 sq mi (1,500 km2)
• Water	32 sq mi (80 km2)  5.4%
Population  (2020)
• Total	405,262
• Density	680/sq mi (260/km2)
Time zone	UTC−6 (Central)
• Summer (DST)	UTC−5 (CDT)
Congressional districts	2nd, 3rd
Website	www.sccmo.org

St. Charles County is in the central eastern part of the U.S. state of Missouri. As of the 2020 census, the population was 405,262,^[1] making it Missouri's third-most populous county. Its county seat is St. Charles.^[2] The county was organized October 1, 1812, and named for Saint Charles Borromeo, an Italian cardinal.

St. Charles County is part of the St. Louis, MO-IL Metropolitan Statistical Area and contains many of the city's northwestern suburbs. The wealthiest county in Missouri,^[3] St. Charles County is one of the nation's fastest-growing counties.

St. Charles County includes a part of the Augusta AVA, an area of vineyards and wineries designated by the federal government in 1980 as the first American Viticultural Area.^[4] The county's rural outer edge along the south-facing bluffs above the Missouri River, is also part of the broader Missouri Rhineland.