Delaware - A Hidden Gem of Real America!
Delaware can be part of a great road trip loop, too.
Start from Philadelpha, and in Delaware follow the signs for US 13 toward Dover. US 13 will take you all the way down the Delmarva (DELaware, MARyland, VA for Virginia) Peninsula, past farmlands, huge chicken-raising industry (Perdue and others) and down to the Chesapeake Bay Bridge/Tunnel.
If you start from DC or Baltimore instead of Philly, you can take the Bay Bridge from Annapolis to Delmarva (Annapolis is another great visit).
From the Norfolk area, you can head east, visit Williamsburg, and then Monticello, and then head up the Blue Ridge Parkway/Skyline Drive along the peaks of the Blue Ridge Mountains toward Front Royal. The whole route is parkland, with Park Service ranger-guided spots along the way. Off the drive are a number of interesting caves as well.
At the north end, you can bend east to DC, explore Virginia's horse country, or head off to Harpers Ferry, Gettysburg, Lancaster and eventually back to Philadelphia.