DC is the most Episcopalian of the metros...ahead of Boston/NYC/Philly. I guess that makes sense that DC is more Protestant, has virtually no WWC and Episcopalianism attracts both northeastern and southern elites.
The Washington National Cathedral is an Episcopal church, so that's not too surprising. It was the denomination of some of the Founders, who were forced to estalish a new church post-Independence because the Church of England cut ties with us. But that's all history and most mainline churches are in communion with each other now.
I'm definitely not part of the elite. I basically joined because I agree with Catholics on a lot of things but am totally out of line with them on social issues, for the most part.