Under Illinois Law, there is no such thing as, "posession is nine - tenths of the law".
According to current public records, the southern boundary of Milennium Park, is the boundary between the villages of Homewood and Flossmoor. This can easily be found by viewing the zoning maps of both towns, or by visiting the Cook County "Cook Viewer" web site. My only interest beyond a tree memorial, and park access, is to have some assurance that repeated and deliberate encroachments across the village boundary onto park district land do not consist of any permanent structures or attempts to create an adverse possession situation. Some adjacent property owners have stated in public records that because they are from Flossmoor, they have an inherent right to adversely possess this land and that everyone needs to just "understand" what they are doing.
This situation was originally created when it was decided in the 1950's not to extend 187th street from Dixie Highway west to Harwood Avenue. Most of the Homewood portion was vacated to property owners in Homewood in 1956, The Flossmoor side was vacated to Flossmoor property owners in 1974. The portion in Homewood that was adjacent to the Hines Lumberyard was not officially vacated until 2006 several years after the property was sold to the Homewood - Flossmoor Park District, and Millennium Park was constructed and opened in 2001. A small portion for a connector street from Downey Road in Homewood, was vacated in 2011.