Milton County, Georgia was created in 1857 on December 18th, from parts of northeastern Cobb, southeastern Cherokee, and southwestern Forsyth counties. Alpharetta was the county seat until the end of 1931, when Milton was merged with Fulton County to save money during the Great Depression. At that time, the Cobb County town of Roswell was also ceded to Fulton, as was Campbell County, giving Fulton its 70-mile long gerrymandered shape along the Chattahoochee River. The cession of Roswell was necessary to make the new county contiguous.

In recent years, some residents unhappy with the distribution of Fulton County's municipal services between urban Atlanta and their northern suburbs have sought to re-create Milton County, consisting of Roswell, Alpharetta, and Mountain Park. The state's constitution however, prohibits any more than 159 counties, the number it has had since 1932.

The picture at left depicts Milton County in 1883, with (counterclockwise from lower right) Gwinnett County to the southeast, Forsyth County to the northeast, Cherokee County to the northwest, Cobb County to the southwest, and Fulton County (Hammond, now Sandy Springs) and DeKalb County (Chamblee and Dunwoody) to the south.