| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 10,159 | 13,673 | 24,256 | |
| 2020 | R | 10,542 | 13,883 | 26,158 | |
| 2016 | R | 8,986 | 12,282 | 23,001 | |
| 2012 | R | 9,883 | 11,096 | 21,441 | |
| 2008 | D | 11,333 | 10,403 | 22,157 | |
| 2004 | R | 8,286 | 11,132 | 19,541 | |
| 2000 | R | 6,481 | 8,617 | 15,523 | |
| 1996 | R | 5,345 | 6,181 | 13,009 | |
| 1992 | R | 5,114 | 5,589 | 13,627 | |
| 1988 | R | 4,234 | 6,923 | 11,222 | |
| 1984 | R | 3,717 | 7,536 | 11,306 | |
| 1980 | R | 3,175 | 6,697 | 11,614 | |
| 1976 | R | 4,458 | 6,470 | 11,082 | |
| 1972 | R | 3,131 | 7,003 | 10,165 | |
| 1968 | R | 2,801 | 5,936 | 9,533 | |
| 1964 | R | 3,694 | 5,053 | 8,747 | |
| 1960 | R | 2,605 | 6,552 | 9,162 | |
| 1956 | R | 1,890 | 6,706 | 8,602 | |
| 1952 | R | 2,287 | 6,628 | 8,932 | |
| 1948 | R | 1,941 | 4,916 | 6,882 | |
| 1944 | R | 2,074 | 5,708 | 7,800 | |
| 1940 | R | 2,277 | 6,330 | 8,632 | |
| 1936 | R | 2,383 | 5,375 | 8,022 | |
| 1932 | R | 2,239 | 5,244 | 7,575 | |
| 1928 | R | 1,371 | 5,965 | 7,369 | |
| 1924 | R | 348 | 4,872 | 6,464 | |
| 1920 | R | 496 | 5,386 | 6,025 | |
| 1916 | R | 1,211 | 5,181 | 6,673 | |
| 1912 | R | 540 | 1,361 | 3,682 | |
| 1908 | R | 587 | 2,805 | 3,688 | |
| 1904 | R | 302 | 3,036 | 3,585 | |
| 1900 | R | 704 | 3,159 | 3,971 | |
| 1896 | R | 657 | 3,111 | 3,846 | |
| 1892 | R | 518 | 1,994 | 2,701 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Boone County sits at the northern edge of the Chicago metro's exurban fringe, where a legacy of factory employment has gradually given way to commuter households. Its R+14.5 presidential margin in 2024 reflects a rural-leaning electorate despite modest population growth.
The county's recent history is a story of close margins. The Democratic margin reached four points in 2008; the Republican margin reached eighty-one points in 1920. Most other elections have been decided by single-digit points.
Boone County's demographics — a population of 53,230, a 72% non-Hispanic-white share, a median household income of $84,571 — situate the county close to national averages on several dimensions. The county's voting pattern over the last decade is most similar to that of Stephenson County and Lee County.