St. Charles County is located in the central eastern part of theU.S. state ofMissouri. As of the2020 census, the population was 405,262,[1] making it Missouri's third-most populouscounty. Itscounty seat isSt. Charles.[2] The county was organized October 1, 1812, and named for SaintCharles Borromeo, an Italian cardinal.
St. Charles County is part of theSt. Louis, MO-ILMetropolitan Statistical Area and contains many of the city's northwesternsuburbs. The wealthiest county inMissouri,[3] St. Charles County is one of the nation's fastest-growing counties.
St. Charles County includes a part of theAugusta AVA, an area of vineyards and wineries designated by the federal government in 1980 as the firstAmerican Viticultural Area.[4] The county's rural outer edge along the south-facing bluffs above theMissouri River, is also part of the broaderMissouri Rhineland.
The County of St. Charles was originally called the District of St. Charles and had no definite limits until 1816 to 1818 when neighboring counties were formed.[5] The borders of St. Charles are the same today as they were in 1818.[6]
St. Charles County is the only known habitat of the threatened decurrent false aster in Missouri.[7]
According to theU.S. Census Bureau, the county has a total area of 593 square miles (1,540 km2), of which 560 square miles (1,500 km2) is land and 32 square miles (83 km2) (5.4%) is water.[8]
The highest elevation is 901 feet (275 m) northwest of Augusta near Femme Osage Creek headwaters.[9]
I-64 – Major freeway in the western portion of the county. Originally U.S. Route 40, the highway was upgraded to Interstate standards in the late 2000s. The highway was re-signed as Interstate 64 from the Daniel Boone Bridge to Interstate 70 inWentzville in 2009.
I-70 – The major east–west thoroughfare in the county. It is mostly a six-lane freeway in the county, but there are sections inSt. Charles andSt. Peters where the Interstate widens to 11 lanes of traffic.
Rte-364 – A freeway in the southern and central portions of the county that begins at Interstate 270 in westernSt. Louis County and ends at Interstate 64 inLake St. Louis.
Rte-370 – A six-lane freeway that connects Interstate 70 in St. Charles County and Interstate 270 in St. Louis County.
St. Charles County, Missouri – Racial and ethnic composition Note: the US Census treats Hispanic/Latino as an ethnic category. This table excludes Latinos from the racial categories and assigns them to a separate category. Hispanics/Latinos may be of any race.
As of 2020, there were 405,262 people and 150,668 households residing in the county. The population density was 643 inhabitants per square mile (248/km2). There were 161,144 housing units. The racial makeup of the county was 83.8%White, 5.2%African American, 0.1%Native American, 2.8%Asian, 0.1%Pacific Islander, and 6.5% from two or more races.Hispanic orLatino made up 4.0% of the population.[25]
There were 101,663 households, out of which 40.50% had children under the age of 18 living with them, 63.20% weremarried couples living together, 9.20% have a woman whose husband does not live with her, and 24.20% were non-families. 19.40% of all households were made up of individuals, and 5.90% had someone living alone who was 65 years of age or older. The average household size was 2.76 and the average family size was 3.18.
In the county, the population was spread out in age, with 29.00% under the age of 18, 8.20% from 18 to 24, 32.60% from 25 to 44, 21.60% from 45 to 64, and 8.80% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 97.10 males. For every 100 females age 18 and over, there were 94.10 males.
The median income for a household in the county was $71,458, and the median income for a family was $64,415. Males had a median income of $44,528 versus $29,405 for females. Theper capita income for the county was $23,592. 4.00% of the population and 2.80% of families were below the poverty line. Out of the total people living in poverty, 4.90% are under the age of 18 and 5.10% are 65 or older.
St. Charles County has had one of the fastest-growing populations in the state for many decades, with 55% growth in the 1970s, 48% in the 1980s, 33% in the 1990s, and another 27% in the 2000s. The county sits at a cross-section of industry, as well as extensive retail and some agriculture. With theMissouri River on the south and east and theMississippi River on the north, the county is bisected east to west by Interstate 70. AfterSt. Charles Airport closed in 2010, the county has one remaining small airport,St. Charles County Smartt Airport. Two ferries cross the Mississippi River from St. Charles County.
St. Charles County is governed by a county executive and a county council. The county council consists of seven members, each elected from various districts in the county. The county executive is elected by the entire county. The current executive is Steve Ehlmann. He was preceded by Joe Ortwerth, who was preceded by Gene Schwendemann, the first county executive of St. Charles County under the new form of government. The executive under the old form of county government was termed a "judge." The county had 258,525 registered voters as of March 2016.[28]
St. Charles County Ambulance District (SCCAD) is the largest such district in Missouri, serving all of St. Charles County and its population of nearly 370,000.
The St. Charles County Sheriff's Department (SCCSD) is responsible for court services and security, prisoner transport,civil process, andbailiffs. Until the end of 2014, SCCSD was the primary law enforcement agency serving unincorporated areas of St. Charles County. On January 1, 2015, the St. Charles County Police Department was established and assumed that responsibility.[29] It should not be confused with theSt. Charles City Police Department. The St. Charles County RegionalSWAT Team is made up of officers from each county law enforcement agency.
In May 2022, Ryan Keuhner, who was then an SCCSD deputy, shot and killed his neighbor's 3-year-old rescue dog with apellet gun. The shooting was reportedly unprovoked and Keuhner was off duty at the time. Video of the dog's owner confronting Keuhner was uploaded online, and later gained national coverage. Keuhner resigned in June 2022 and was charged with a class Amisdemeanor for animal abuse.[32][33]
In 2023, the county council issued a resolution aimed at library policies and staff online activities. The resolution followed protests and comments at council meetings from residents who complained about a staff member wearinggender non-conforming clothes. Within the resolution, the council asked the library CEO to remove an article they shared on their personalLinkedIn profile related to conservative campaigns targeting public libraries andfreedom of speech.[34]
TheRepublican Party predominantly controls politics at the local level in St. Charles County. Republicans hold all the elected positions in the county.[35][36][37]
District 64 –Deanna Self (R-St. Paul, since 2025). Consists of Flint Hill, Josephville, St. Paul, and parts of Foristell, O'Fallon, and Wentzville.
District 65 –Wendy Hausman (R-St. Peters, since 2023). Consists of West Alton, Portage Des Sioux, and parts of Cottleville, St. Charles, and St. Peters.
District 69 –Scott Miller (R-St. Charles, since 2025). Consists of parts of St. Peters and Weldon Spring.
District 102 –Richard West (R-Wentzville, since 2021). Consists of Augusta, Defiance, New Melle, Weldon Springs Heights, and parts of Cottleville, O'Fallon, St. Peters, and Weldon Spring.
District 103 –Dave Hinman (R-O'Fallon, since 2023). Consists of part of O'Fallon.
District 104 –Terri Violet (R-St. Peters, since 2025). Consists of part of St. Charles and St. Peters.
District 107 –Mark Matthiesen (R-O'Fallon, since 2023). Consists of parts of Dardenne Prairie and O'Fallon.
District 108 –Mike Costlow (R-Dardenne Prairie, since 2025). Consists of Lake St. Louis and parts of Dardenne Prairie and O'Fallon.
St. Charles County is divided into three districts in theMissouri State Senate, each of which are represented by Republicans.
District 2 –Nick Schroer (R-Defiance, since 2023). Consists of the communities of Augusta, Cottleville, Dardenne Prairie, Defiance, Josephville, Lake St. Louis, New Melle, O'Fallon, St. Paul, Weldon Spring, and Weldon Spring Heights.
District 10 -Travis Fitzwater (R-New Bloomfield, since 2023). Consists of the communities of Flint Hill, Foristell, and Wentzville.
District 23 –Adam Schnelting (R-St. Charles, since 2025). Consists of Portage Des Sioux, St. Charles, St. Peters, and West Alton.
Donald Trump won the most votes in St. Charles County, with 41.50 percent. U.S. SenatorTed Cruz (R-Texas) came in second with 38.87 percent, GovernorJohn Kasich (R-Ohio) placed third with 10.70 percent, and U.S. SenatorMarco Rubio (R-Florida) was fourth with 7.10 percent.
Former U.S. SenatorRick Santorum (R-Pennsylvania) won the most votes in St. Charles County, with 56.29 percent. Former GovernorMitt Romney (R-Massachusetts) came in second with 25.43 percent, and former U.S. RepresentativeRon Paul (R-Texas) was third with 12.69 percent.
Democratic
With incumbent PresidentBarack Obama facing no serious opposition, few St. Charles County voters voted in the Democratic primary; Obama won 87.83 percent.
Former GovernorMitt Romney (R-Massachusetts) won the most votes in St. Charles County, with 37.72 percent. U.S. SenatorJohn McCain (R-Arizona) came in second with 34.95 percent, former GovernorMike Huckabee (R-Arkansas) placed third with 21.83 percent, and U.S. RepresentativeRon Paul (R-Texas) was fourth with 3.83 percent.
Former U.S. SenatorHillary Clinton (D-New York) received a total of 23,611 votes, more than any candidate from either party in St. Charles County during the 2008 presidential primary.
The Westplex is part of St. Charles County that used to be called "The Golden Triangle". The "triangle" was formed by I-70 to the north, Missouri Route 94 to the southeast, and I-64 to the southwest. Since almost all of the growth in St. Charles County was within this triangle it was dubbed the "Golden" area of St. Charles County, hence, Golden Triangle. Today the Westplex is made up ofSt. Charles,St. Peters,Weldon Spring,Cottleville,Dardenne Prairie,O'Fallon,Lake St. Louis, andWentzville.
^Bryan, William S. (1993).St. Charles Co., Missouri: biographical sketches from pioneer families of Missouri by Bryan and Rose. Baltimore, Maryland: Genealogical Publishing Company. p. 1.
^"County Council".St. Charles County, Missouri. RetrievedMarch 9, 2022.
^"Assessor".St. Charles County, Missouri. RetrievedMay 15, 2024.
^Korando, Russell (November 23, 2012)."St. Charles County judge nominated for prosecutor".St. Charles County Suburban Journal. RetrievedDecember 3, 2013.Ehlmann was required to appoint someone from the same political party as Banas, a Republican, to serve until the office comes up for election in November 2014.