[2] The county was formed in 1820 and named for Colonel John Grant,[3] who led a party of settlers in 1779 to establish Grant's Station, in today's Bourbon County, Kentucky.

Grant County is included in the Cincinnati-Middletown, OH-KY-IN Metropolitan Statistical Area.

[5] The Grant County News, established in 1906 and published in Williamstown, is preserved on microfilm by the University of Kentucky Libraries.

The microfilm holdings are listed in a master negative database on the UK Libraries Preservation and Digital Programs website.

19.80% of all households were made up of individuals, and 8.20% had someone living alone who was 65 years of age or older.

Grant County has six schools: Crittenden Mt Zion (CMZ), Dry Ridge Elementary (DRE), Sherman Elementary (SES), Mason Corinth Elementary (MCE), Grant County Middle School (GCMS), Grant County High School (GCHS) and Williamstown Independent Schools (WES)- (WMS) – (WHS).

[18] Grant County, specifically in Williamstown, is the location of the Ark Encounter, operated by the Christian apologetics organization Answers in Genesis and opened in 2016.