My 2 past trips:
1 - 2008 - Massachusetts (50 miles West of Boston) along I-90 to Yellowstone, stopping in the Badlands, Devil's Tower (Wyoming), and Glacier National Park. Forget how long it was - beautiful drive after you got West of Chicago.
2 - 2009 - Mass. to Gettysburg, D.C., Quantico (National Museum of the Marine Corps), Charleston, Parris Island (Marine Corps Recruit Depot), to Orlando, then Pensacola, up to the Great Smoky Mountains National Park.
3. 2010 - Mass. out to the Denver area (JOB INTERVIEWS!!!!!!) up through Wyoming, cross the Continental Divide, into Grand Teton National Park, then back into Yellowstone. Man I cannot wait.......
Each trip is about 2,400 miles or so one way.