I recently reviewed the big firms' websites (V100) in Chicago to see who actually placed their graduates as partners and associates. It seemed that I saw as many people from Michigan as I did from Northwestern. The geographic distance didn't seem to hurt Michigan. UIUC was only slightly behind these two. Less people from Chicago, but we're simply talking about sheer number, and Chicago's class size is smaller and probably more geographically dispersed.
WUSTL seemed to have a semi-strong presence, Notre Dame a little less so (also probably due to geographic dispersion rather than class rank-based placement). Kent, DePaul and Loyola seemed to come next. Everything else seemed to simply be a smattering (Minnesota, Iowa, Wisconsin, OSU, Bloomington, Case), and the people from these schools that got in were all cum laude and on law review.
But I think a lot of this is self selection. I think the TLS community is different from average law school applicants. Most people tend to go locally and return locally, and don't really consider moving across the country to go to law school and then moving again for their first job. There's a lot more self-selection region-wise than people acknowledge, so placement by sheer numbers isn't going to mean much. Probably close to all the top 5% graduates from Kent, DePaul and Loyola stay in the city, whereas the top 5% from everywhere else more readily stay in the market closest to their school. Not everyone from the region is shooting for Chicago biglaw. I think a lot of the best-in-state public schools place a lot of people in the top firms in the bigger, medium-sized, or even smaller cities within that state -- which don't qualify for biglaw, but do give you a decent midlaw salary. So, from the Minnesota, Iowa, Wisconsin, OSU, Bloomington crop, at least, their placement is not necessarily worse, it's just that less people from these schools have a connection to Chicago or really want to live and work there.
If you really want to know how well a school places in a region, go to the law school's website and see how many top firms from the region participate in OCI there. Most schools have something like this, but you have to watch the wording of their OCI lists. Some list firms that only occasionally participate. Wisconsin has a list of only firms that participated in 2009 and each firm's interview criteria. Seemed like most biglaw firms have a cutoff of around top 25% there, with the exception of Jones Day, which is top 15% (and all wanted law review or moot court). But not very many from Chicago participated this year. It was mostly biglaw from Minneapolis and Milwaukee. My bet is that the prospects for Chicago are similar at the other Big-Ten state schools with similar rankings (shitty this year, but in general, top 20-25% will get you an interview). How many people end up going into Chicago biglaw after this probably dependent on desire and on their interviewing skills.