Clay County was created on June 16, 1870, and was named in honor of the Kentucky statesman Henry Clay.

Morgan County was originally created in 1817.

Overton County was established in 1806 and named in honor of John Overton.

Pickett County was formed in 1879 from portions of Overton and Fentress counties.

Created in 1806, the county is named in honor of Arthur Campbell.

The county was established in 1823 from Morgan, Overton, and White counties and is named in honor of James Fentress.