My problem is that I have a site which has requires a dedicated page for every city I choose to support. Early on, I decided to use subdomains rather than a directly after my domain (ie i used la.truxmap.com rather than truxmap.com/la). I realize now that this was a major mistake because Google seems to treat la.truxmap.com as a completely different site as ny.truxmap.com. So for instance, if i search "la food truck map" my site will be near the top, however, if i search "nyc food truck map" im no where in sight because ny.truxmap.com wouldnt be very high in the page rank by itself, and it doesnt have the boost that it ought to be getting from the better known la.truxmap.com

So a mistake I made a year ago is now haunting my page rank. I'd like to know what the most painless way of resolving my dilemma might be. I have received so much press at la.truxmap.com that I can't just kill the site, but could I re-direct all requests at la.truxmap.com to truxmap.com/la and do the same for all cities supported without trashing my current, satisfactory page rank results I'm getting from la.truxmap.com ??

EDIT I left out some critical information. I am using Google Apps to manage my domain (that is, to add the subdomains) and Google App Engine to host my site. Thus, Google Apps provides a simple mechanism to mask truxmap.appspot.com (the app engine domain) as la.truxmap.com, but I don't see how I can mask it as truxmap.com/la. If I can get this done, then I can just 301 redirect la.truxmap.com to truxmap.com/la as suggested below.

Thanks so much!