Legal Question in Real Estate Law in Illinois

It depends. if the other owners knew the garage was on their property and did nothing then it may have been long enough for you to have "acquired" the land the garage sits on. My suggestion would be to get a survey done to be sure it is on someone else's land first. In order to keep your current neighbor from tearing the garage down you would have to go to court and prove that the prior neighbors knew the garage was on their land and didn't contest, which means you'd have to contact all of your prior neighbors and get their testimony in court or their sworn statements in affidavits.