The county was named for Duncan G. Campbell, one of the U.S. commissioners responsible for the Treaty of Indian Springs.
When the Atlanta and West Point Railroad began to plan its route, the town's residents said no due to noise concerns, and the tracks were laid through Fairburn instead, which flourished while Campbellton died out, and Fairburn became the county seat in 1870.
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 legislation creating the merger was enacted on August 9, 1929, with Milton being added to the process in 1931.
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