I've never been to Philly, but I agree about DC and almost added that to my list, but there are too many places there to name. However, we did get a White House tour when we were there and that more than qualifies and I should have mentioned it.
I've been to a lot of places around the US and DC had by far the best food (besides for Louisiana). Better than New York and certainly better than Chicago. They only other place that I really really enjoyed all the food we had was San Diego.