September is a good month on the east coast. Nice weather, the kids are back in school, campgrounds and attractions are not as crowded.
Definitely stop and see the
Flight 93 Memorial near Somerset PA.
And, if possible, stop at Pottsville PA and tour the
Yuengling Brewery. It's America's oldest brewery. Even if you don't care for beer, it's a very interestig tour.
The
Three Mile Island Nuclear Plant is just south of Harrisburg PA.
And the
Rockville Bridge is just outside Harrisburg. It's the longest stone arch bridge in the world.
And of course, Philadelphia, PA.
The
Chesapeake & Delaware Canal is in northern Maryland.
There is a lot to see, start planning your stops now.
Enjoy your trip.