You've got to do some digging. Boarded up windows and overgrown lawns are great indicators of abandoned properties, but sometimes these rundown structures are merely 'vacant,' and the owners still very much want to keep their decrepit investment. Most potentially abandoned buildings are reported to the city itself using Chicago's 311 system, and all these reports can be found on the Chicago Data Portal (our map tool pulls some of its data from these reports). However, these calls are only warning signs that someone noticed something odd about the place: they're far from proof that no one's claiming it.
In order to figure that out, you'll need to figure out who currently holds the deeds and titles to the property you're interested. A fantastic resource to use for this process is found on the city's main website: Check Status of Vacant Property
Here
If you can't find any information there, try
cookcountypropertyinfo.com, where several major city departments keep an aggregated collection of tax information on individual parcels of land within Cook County. If those fail, you'll need to get creative! Try the methods described in this article.