Austell Road in southern Cobb County has changed dramatically since it first went under state control. Located in older suburbs northwest of Atlanta, the changes to the area around it as well as the road itself have been dramatic. First, it was a rural farming area, then an early suburb and now a heavily urbanized area that is facing the difficulties of its age and major demographic change.

Old GA 340 extends from Atlanta Road (Old GA 3) between Marietta and Smyrna and Bankhead Highway (U.S. 78/278/GA 8) east of Austell. While it is GA 5 today except for a small county-maintained portion, Austell Road began its existance as a state route as GA 340. In all, the former highway extended 8.7 miles with 0.4 of those miles now under the jurisdiction of Cobb County. In purpose, Austell Road serves as the only truly direct link between the county seat of Marietta and the city of Austell to the southwest.

GA 340 was first established in 1961 along what was then a two-lane county road. The era when the route was established was during a time of major growth in the area, and the route became a core for schools, businesses, subdivisions and hospitals. Regardless of the growth, GA 340 remained a two-lane highway largely unchanged during its existance. In fact, the only major project along the route consisting of a new railroad grade separation and interchange over Bankhead Highway (U.S. 78/278) that was completed in 1980. Eventually, Austell Road outgrew the GA 340 designation and became part of GA 5 on June 14, 1983 when GA 5 was relocated from Powder Springs Road to the northwest.

While the route only lasted 22 years, further changes occured along the route that included a full-scale widening of the highway completed in the early 1990's. The decommissioning of the northernmost portion occured after the road became GA 5. That occured when GA 5 was relocated to part of South Cobb Drive (GA 280) upon completion of the reconstruction of a semi-interchange and railroad tunnel north of the route in 1989.

This 1973 map shows GA 340 and GA 5 on its former alignment through Powder Springs prior to the 1983 relocation. Note the northermost section extending to Atlanta Road that is no longer state-maintained.