When I do a "people" search from the advanced search page and choose District of Columbia, only my own name comes up. When I choose Washington, DC (which also seems to be one of the choices), I get absolutely nothing.
In the early days, I added a geographic area to my profile (the drop-down uses "District of Columbia) and saved it, but the next time I logged out and in, it had disappeared. It took me a few tries over the first week to put in the information and have it stick.
If you added in DC as your geographic area early on. you may need to put it in again. On the other hand, if you left it blank because that' was too much information to share right off, I can understand. This is an adventure for us all. I just feel strange about being the only one.