I don't remember ever eating at Casey's Drive In as a kid, although I was certainly aware of it, as it was located across from Westgate Shopping Center at 2519 21st Street. The restaurant first appeared in the phone book around 1968, with locations at 1390 N. Ridge Road (across from O'Neil's) and at 4835 Liberty Avenue in Vermilion. The 21st Street store in Lorain followed in 1969. There were Elyria locations as well.
The ads for this chain are interesting, because the Elyria phone book ads featured a photo of a real live "Casey" dressed in an old-time baseball uniform leaning on a bat, and the Lorain phone book ads featured a cartoon ballplayer mascot holding up a hamburger. I liked the cartoon mascot a lot, but apparently not enough to eat there!
I haven't been able to find out much about the restaurant chain. It probably was a regional endeavor... but I'll keep Googling until I find something.
Although Casey's was not in the same league as McDonald's, the chain must have had a pretty successful formula. The 21st Street store lasted almost 20 years, finally closing around 1987. Pine Gardens restaurant replaced it at the location and is still in business today.