I grew up on a farm in SE PA in the 1960s & early 1970s.
We had wild pheasants galore, and loads of doves, and rabbits were abundant.
But I only recall hearing bobwhite calling one time on our farm, and never heard or saw them anywhere else around there.
I heard bobwhite calling in Blair County in the 1990s. I don't know if they were wild or stocked.
There are quite a few quail at Cape Henlopen State Park in Delaware. We stayed at the campground there, and was very happily surprised to here quail calling there. The quail there live in a band of brush between the sandy beach and the uplands with pine trees, which is where the campground is located.
I read that there are quite a few quail in the same sort of habitat in New Jersey, in the brushy land back from the beach, where that land has not been developed.