Being a West Coast based gal, I would recommend Yellowstone National Park and the Grand Tetons. There is limited travel in the winter (think you have to sign up for snow coaches in Yellowstone) but the summers present easy accessibility. Don't try to see everything in 1 day, either!
I’ve learned that people will forget what you said, people will forget what you did, but people will never forget how you made them feel. –Maya Angelou