How To Tell Them Apart
Size. Chipmunks are the smallest of the 3 kinds of animals. They are noticeably smaller. Ground squirrels are not good climbers. Fox Squirrels are terrific climbers and you'll see them navigating fences, trees and dumpsters with ease. Chipmunks can scale anything too. They'll zip up the side of a cabin like they have super powers.
Tails. Between ground squirrels and fox or eastern squirrels, the tail is distinguishable. Ground squirrel tails are not bushy, while fox and eastern squirrels will be.
Color. Between eastern and fox squirrels, the obvious way to tell them apart is by color. Fox squirrels are much more copper/orange-ish while eastern squirrels are predominantly gray and white.