Ahh, makes more sense with the additional context. Working with those parameters in mind... Kent Falls/New Milford (CT), and Great Barrington/Stockbridge/Lenox (MA) are both potentially interesting road trips through quaint pockets of lower NE just around the 4-hour mark. I have also heard good things about Lititz (PA), Annapolis (MD), and Milford (PA)...but haven't visited those three yet.

Genuinely curious/not trolling - is it intentional the trips are all inside PA? You've already gone to Reading, Jim Thorpe, Hershey and Stroudsburg ...and are now considering ...Harrisburg. DC and NYC are similar driving distances and (basically objectively) infinitely more interesting than all of these places combined. You liked Pittsburgh so it doesn't sound like you have an emphasis on smaller towns.

Also, is the 4-hour cap really crucial? A small amount more driving gets you to Newport RI, Vermont, coastal NH, Boston, the Berkshires in CT/MA, or even Williamsburg.

Alternatively, similar travel time involving an airplane and you can cheaply get to places like Charleston (2:00 $350), New Orleans (3:20 $400), Florida (3:00 $115), Denver (4:00 $210) or Chicago (2:30 $200).

Best of luck with whatever you decide.