Campbell County was formed by the Georgia legislature on 20 December 1828. The county was formed from Carroll, Coweta, DeKalb and Fayette counties. The county was named after Duncan G. Campbell, who was one of the United States Commissioners who signed the Treaty of Indian Springs Acquisition.
The county existed for one hundred and four years. The northwestern half of Campbell (and a bit more of Carroll) became Douglas County in 1870, divided on October 17 at the Chattahoochee River. The remainder of Campbell County was ceded to Fulton County at the end of 1931, along with Milton County, to save money. The legislation creating the merger was enacted on August 9, 1929, with Milton being added to the process in 1931.
NOTE: Information from https://sites.rootsweb.com/~gacampb2