Cottonwood trees have slightly dentate (toothed) margins. Also, their leaves tend to turn more yellowish during fall senesence.
This looks an awful lot like the species I study, Chinese tallow tree (Sapium sebiferum). Native to China and much of southeast Asia, it was introduced into Georgia in the late 1700s by Ben Franklin. It is a problematic invader throughout much of the southeastern US and has been listed as a noxious weed in Florida.
I agree that it has pretty fall foliage, especially for the south where we don't get much for autumn color. That's one of the reasons it continues to be widely planted.
Sorry to be such a botany geek, but this little beast has been quite the cottage industry for me the past several years.