If your looking for a great street level experience try Boston & Philadelphia, the old Colonial sections of the town are awesome. Very Americana. If I were to choose which one to go to next it would have to be Boston. Reasons being that most of the city is safe, Philly not so much. Other than that they both have a great deal of history related to the American Revolutionary War.
Haha, I was just about to say that Boston had a horrible street level experience. Really windy, you can't see much because of the buildings blocking your view and it's pretty... dull to be honest. Doesn't help that people aren't very friendly either