It should state where the passport comes from. I live in Illinois and used a post office in one of the suburbs to do my passport, and it states Chicago in it, so take another look, you should have a city listed also.
It's the passport office that issued the passport. Our last ones were New Orleans because the Philadelphia office was closed to put in a new computer system. The current ones are Philadelphia. USUALLY it's the office closest to your home, geographically.
Showing you that even "old timers" learn something, it is not just the "newbies", I never noticed that before! :-)
I just looked at the one I just got, plus the old one they sent back and it just says National Passport Center. Is that Philadelphia??? Talk about brain cramp, I don't even remember where I mailed it! I am scarey sometimes, amazing that I get by when I travel all over!!! :-)