There are about a half dozen subspecies of the common rat snake, Pantherophis obsoletus (formerly Elaphe obsoleta). There is a range map at http://people.wcsu.edu/pinout/herpetology/eobsoleta/.

I've only kept the black rat snake subspecies, but friends have kept Texas, yellow, and Everglades subspecies. Wild caught adult Texas and yellow rats are a bit more excitable than black rats, but IMO, just about any of the P. obsoletus subspecies can make an excellent pet if you start with a baby and handle daily for around 5 minutes (skip handling for 48 hours after feeding). Common rat snakes get bigger than corn snakes, but care is the same as that of an equal sized corn snake.