[3] It is named for John Hardin, an officer in the American Revolution.

[5] At the 2000 census,[10] there were 31,945 people, 11,963 households and 8,134 families living in the county.

26.50% of all households were made up of individuals, and 10.80% had someone living alone who was 65 years of age or older.

As of the 2010 United States Census, there were 32,058 people, 11,762 households, and 7,950 families living in the county.

There were 13,100 housing units at an average density of 27.8 per square mile (10.7/km2).

The last Democrat to win the county was Lyndon B. Johnson in his 1964 landslide.

Ada Airport (FAA LID: 0D7) is a privately owned, public-use airport located one nautical mile (1.85 km) northwest of the central business district of Ada, a village in Hardin County.

Hardin County Airport (FAA LID: I95) is the largest paved facility and is located 3 miles south of Kenton, Ohio on CR 135.

WOCB-LP TV48 is a local Christian television station in downtown Kenton covering channels 39.1-39.4.