Chicago, Illinois and Atlanta, Georgia are 719 miles apart. A city located halfway between them would be Bonnieville in Kentucky.
Seminole, OK. The nearest city is OKC.
Interstate 35, Guthrie, OK 73044.
Philladaliphia
The halfway point from Traverse City, MI. and Atlanta GA. would be Cincinnati, Ohio.
Kalamazoo
The half way from Iowa city IA to Chicago, IL is Davenport.
The city of Anchorage in Alaska is roughly halfway between Sydney and Chicago, in terms of distance. However, since there are no direct flights between Sydney and Anchorage, it may not be the most practical midpoint for travel purposes.
Atlanta
Elk City, OK
Interstate 75, Berea, KY 40403
Caryville, TN is a little over halfway but you don't have to get off the interstate.