[2] The county was created on February 26, 1856, and named after Andrew Jackson Miller (1806–56), president of the Medical College of Georgia.

[4] The majority of Miller County, west of a north-to-south line made as a continuation of the eastern Early County border, is located in the Spring Creek sub-basin of the ACF River Basin (Apalachicola-Chattahoochee-Flint River Basin).

The county's very northeastern corner is located in the Ichawaynochaway Creek sub-basin of the same ACF River Basin, while the southeastern portion, from just north of State Route 91 going south, is located in the Lower Flint River sub-basin of the same larger ACF River Basin.

[5] As of the 2020 United States census, there were 6,000 people, 2,333 households, and 1,556 families residing in the county.

The Miller County School District operates public schools serving residents of the county.