Marietta, Georgia, on Highway 41. The 1970 greeting says:

“Hi Peoples! We are enjoying our stay here Hope the weather has warmed a little we see Min and Walt pretty near every day. Lassilus are leaving to-day. Raingin to day, we got to the ocean a lot, butnot swimming yet, water too cold. See you, Chubby”

The ocean? Marietta is in the middle of the state. And the state is Georgia, which is not exactly known for is Gulf ports.