It is named for Alexander Hamilton, Revolutionary War hero and the first United States Secretary of the Treasury.

[3] On March 18, 1925, the infamous Tri-State Tornado tore across the county, destroying dozens of homes and farms in Flannigan, Twigg, Mayberry, and Crook townships, and killing 37 people.

Not until 1920, when isolationist sentiments turned many voters against the party of Woodrow Wilson, did Hamilton County vote Republican, and Herbert Hoover was to carry the county in 1928 due to anti-Catholic sentiment against Al Smith.

From 1940 onwards, when Wendell Willkie carried the county due to opposition to involvement in World War II, Hamilton has become increasingly Republican.

Although Lyndon Johnson, Jimmy Carter in 1976 and Bill Clinton in 1992 all gained absolute majorities for the Democratic Party (with Michael Dukakis losing the county by just four votes in 1988), a rapid swing to the Republicans has taken place since 1992.