I can think of four.
1) In Limo One is Missing they mentioned the Pennsylvania Turnpike.
2) Can't think of which episode but Rosco got the state pen (penitentiary) mixed up with Penn State. (Just to clarify, I've been to Penn State, not the state pen lol)
3) They mentioned Detriot when talking about Coy's old job.
4) I flew into often mentioned Atlanta on the way to USMC boot camp in 1978.