The lower 48 plus Hawaii and Alaska.
Then there are the ‘territories’: Puerto Rico, Guam, the Northern Mariana Islands and the U.S. Virgin Islands (according to http://www.reference.com/geography).
I’ve been to:
Hawaii, Illinois, New Hampshire, Vermont, Maine, New York, Massachusetts, Connecticut, Rhode Island, North Carolina, South Carolina, Florida, Utah, Colorado, Nevada, Arizona, California, Virginia, West Virginia, Pennsylvania, Maryland, Delaware, New Jersey. (Okay, I’ve “passed through” a few, not exactly ‘visited’)
I think it would be a wonderful experience to take a road-trip to (and sight-see) all the 49 states – preferably with a 5th-wheel!! (and a good travel partner). No road trip to Hawaii but…I did hike throughout five of the eight islands! And, did you know, that Hawaii is the most isolated population center on the face of the earth?? (per http://www.50states.com/facts) It FELT very isolated too. I remember feeling, “it’s a nice place to visit but I wouldn’t want to live here”.