The Bears are a rather interesting case.
The City of Chicago screwed up when they decided to "renovate" Soldier Field by building a new stadium within the shell of the old one. The new stadium is crap, and Soldier Field lost its historic landmark status, to boot. So, now the Bears are looking for a new stadium. The City doesn't want them to leave, but Chicago doesn't have the money to build a new stadium.
The Bears purchased the old Arlington Park horse racing facility in the suburbs, and planned to build a new stadium there using their own funds, but were going to need the state to help out on infrastructure (roads and such) and some kind of tax deal (presumably an abatement, or, perhaps, what we would call a TIF district) in order to make the new site viable, but the State of Illinois is broke (thanks to ridiculous pensions and graft) and, so far, has made no move towards helping the Bears with the aspect of the project.
Thus, the Bears are now turning to the State of Indiana, which is not broke, and sits about 20 miles from downtown Chicago.
I think the Bears would still prefer to build their own stadium at Arlington Park, but if Illinois isn't going to do what they want, they will see if they can get that from Indiana.