The outer banks, New Orleans, Aspen.
Alaska, Charleston, San Antonio.
Happy to see both Alaska and Seattle (the gateway to Alaska) on so many lists! 
Mr. says he wants to travel internationally when we retire. I keep telling him that we have not been to so many states, so exploring the middle and the south parts of the US is on my list. Cheaper and faster to get to!
Alaska (Denali), Marfa, TX (Marfa Lights and the Chianti Foundation), Florida Keys.
Hawaii, Puero Rico, San Francisco
Alaska, Florida keys, the great middle/north of the country that I haven’t visited, especially the Dakotas.
Colorado, Oregon, Washington.
Alaska, Bryce and Zion, New Orleans
@doschicos We went to Vegas for a family vacation spur of the moment long story kind of thing with the 3 kids (pre-teen to teen at the time) and absolutely loved it. It was a big surprise. And we didn’t do a lick of gambling.
Montana, Idaho, Washington State…a roadtrip that is definitely on my bucket list.
Sea Islands (and Charleston and/or Savannah), Jackson Hole/Yellowstone, Austin. And probably Hawaii.
Las Vegas – I was there for one evening, and won’t likely be back again. I had the best Japanese meal ever in some commercial area a few miles from the Strip, but the Strip itself was beyond depressing.
American side of Niagara Falls – The Cave of the Winds is fun, or at least it used to be, but you can barely see the Falls from the American side. You shouldn’t feel deprived if you only visited the Canadian side; that’s the side worth visiting.
New Orleans, Savanah and the Keys in Florida
I’ve been up and down both coasts (and would love to go back to some of those places). As for places I’ve never been, it would have to be some places in between. New Orleans, Colorado and if my D ends up at grad school there, I will definitely want to visit St. Louis.
@doschicos - H and I never had any desire to visit Las Vegas either, but decided to try something new last June. It was hot and yes there are less than nice areas, but we actually had a great time. There was so much to do and see — and like mom23travelers we didn’t gamble a single dime.
Pacific Northwest, Maine, Sante Fe
@Bromfield2, my son got married in Maria, Tx in April! We really made the most of our time in that part of the country. Post-wedding, we spent 5 days hiking in Big Bend NP and loved that too.
Alaska, Hawaii, and Seattle.
Alaska, Hawaii, Outer Banks
The Painted Desert in Arizona!
New York City, Everglades, Glacier National Park
Feeling lucky that I’ve been to most of the places people are listing. Sure wouldn’t mind going back to many of them, though.
I was thinking the same thing…it’s also bringing back some great memories of those places.
Midway Atoll, Guam, Moab
Nashville, New Orleans, Tuscaloosa