How Did I Not Know About This?!

"The Silver Comet Trail is located 13 miles northwest of Atlanta, Georgia. It's free of charge, and travels west through Cobb, Paulding, and Polk counties. This quiet, non-motorized trail is for walkers, hikers, bicyclists, rollerbladers, horses, dog walkers, and is wheelchair accessible."

You can ride a bike from Cobb to Alabama (and then some more along the Chief Ladiga Trail)! I had heard of the Silver Comet Trail but I assumed it was like one of those trails that runs along the river for a short distance.

A writeup on the trail at Lonely Planet.