Hardin was murdered by Shawnee Indians while he was on a peace mission in 1792 for President George Washington, in what is now Shelby County, Ohio.

In the 1790s and early 1800s, the Hardin County area, especially Cave-In-Rock, was notorious as a stronghold used by outlaws, bandits, river pirates, and counterfeiters.

Most geologists accept the theory that the older rocks at the center of the uplift are a result of this deep-seated igneous activity.

[12] In its early history, Hardin County was opposed to the “Yankee” Republican Party and its Civil War against the South – with whom it was closely allied both culturally and economically.

Like the nearby counties of Johnson, Massac and Pope, it managed to remain loyal to William Howard Taft during the 1912 election when the Republican Party was mortally divided.

Hardin County would next be carried by a Democratic presidential candidate in Franklin D. Roosevelt’s 1932 landslide victory, and not after that until Lyndon Johnson in 1964.

Nonetheless, since 2000 Hardin County has followed the same political trajectory as Tennessee, Missouri, Kentucky, West Virginia and Appalachian regions of adjacent states, whereby the Democratic Party's liberal views on social issues have produced dramatic swings to the Republican Party amongst its almost entirely Southern white population.

[15] The past six Presidential elections have observed a swing totalling 79 percentage points to the GOP, with Hillary Clinton in 2016 receiving barely half the proportion of the worst-performing Democrat from before 2010.