Categories by State

I have a bit of a dilemma here...I'm working on building my classifieds site and I want a "home page" for each state that shows all the subcategories under that state. I'd like to promote the site by state using a shortened URL - for instance www.mysite.com/mi would show all the categories/subcategories and listings for Michigan. I know this is possible by entering the state as the parent category, then adding all the subcategories with different keys under each state. But I have a total of 85 subcategories (at least) that would need to go under each state! Inputting 4,250 subcategories total would take quite some time(although I'm sure there is a way I could do an import directly into the database as well). Is there a way to do this using a search string? Right now when you do a search by state it will just show ALL the listings grouped together in the results, I don't want that, I'd like to see all the categories for each state selected instead.

Has anybody else done anything like this? If so how did you accomplish this?

Thanks!

Hmm, I may have posted too soon...

I think I just figured out how I can do this using content boxes rather than entering 4,000+ categories. Looks like I'll have to make a PHP content box for each state. Anybody have any experience with the Field-bound Boxes plugin? That looks like something I might be able to use to do this.