| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 92,226 | 130,588 | 227,408 | |
| 2020 | R | 89,530 | 128,389 | 222,566 | |
| 2016 | R | 68,626 | 121,650 | 203,184 | |
| 2012 | R | 71,838 | 110,784 | 186,366 | |
| 2008 | R | 84,183 | 102,550 | 188,529 | |
| 2004 | R | 66,855 | 95,826 | 163,488 | |
| 2000 | R | 53,806 | 72,114 | 128,686 | |
| 1996 | R | 41,369 | 47,705 | 102,246 | |
| 1992 | R | 37,263 | 38,673 | 106,563 | |
| 1988 | R | 29,286 | 50,005 | 79,500 | |
| 1984 | R | 17,617 | 47,784 | 65,401 | |
| 1980 | R | 20,668 | 36,050 | 59,768 | |
| 1976 | R | 22,063 | 26,105 | 48,704 | |
| 1972 | R | 11,034 | 25,677 | 36,711 | |
| 1968 | R | 10,374 | 13,533 | 29,659 | |
| 1964 | D | 14,530 | 9,020 | 23,550 | |
| 1960 | D | 11,890 | 10,888 | 22,778 | |
| 1956 | R | 7,618 | 9,462 | 17,080 | |
| 1952 | R | 6,493 | 8,451 | 14,964 | |
| 1948 | D | 6,049 | 5,976 | 12,064 | |
| 1944 | R | 4,880 | 7,050 | 11,966 | |
| 1940 | R | 5,334 | 7,792 | 13,176 | |
| 1936 | D | 5,903 | 5,156 | 12,068 | |
| 1932 | D | 6,911 | 3,664 | 10,737 | |
| 1928 | R | 5,081 | 5,404 | 10,507 | |
| 1924 | R | 2,364 | 4,668 | 7,897 | |
| 1920 | R | 2,472 | 6,645 | 9,213 | |
| 1916 | R | 1,914 | 3,518 | 5,483 | |
| 1912 | R | 1,792 | 2,350 | 4,796 | |
| 1908 | R | 1,979 | 3,480 | 5,538 | |
| 1904 | R | 1,788 | 3,203 | 5,091 | |
| 1900 | R | 2,343 | 3,324 | 5,721 | |
| 1896 | R | 2,448 | 3,173 | 5,651 | |
| 1892 | R | 2,485 | 2,522 | 5,044 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
St. Charles County has been one of Missouri's fastest-growing counties for two decades, fueled by suburban expansion from St. Louis. That population surge has not softened its Republican lean, which held at R+17 in 2024.
The Republican margin in St. Charles County reached its widest at forty-six points in 1984. The margin in 2024 was seventeen points, in line with the county's deep historical pattern.
St. Charles County's loyalty is rooted in its place. Median household income of $104,692, a 84% non-Hispanic-white share, and a population of 414,535 together describe a community whose political habits are deeply settled. The county's voting pattern over the last decade is most similar to that of Clarke County and Antrim County.
