[2] The county was named in honor of Col. John J. Hardin, of Illinois, who was killed in the Mexican–American War.

It was named after Colonel John J. Hardin, who died in the Mexican–American War.

The second courthouse was a two-story building and stood on the site of the current office of the county sheriff.

The structure was listed on the National Register of Historic Places in 1981.

[13] As of the census[14] of 2000, there were 18,812 people, 7,628 households, and 5,087 families residing in the county.

29.40% of all households were made up of individuals, and 15.70% had someone living alone who was 65 years of age or older.

The population ranking of the following table is based on the 2020 census of Hardin County.