The map above shows land acquisition status for the planned third airport for Chicago. The red is the land already required while the green parcels are the land needed for the development of the inaugural two runway airport. The blue shows the land needed for the planned 6 runway airport.
I have been involved with this issue all of my professional career. The first planning document I ever read on the plan was in 1968 when it was planned to be located to the east of the present location. The planning and environmental documents would probably fill a large room. The planned airport is south of Chicago, with access planned from I-57 and IL Route 50.
The planning for the airport was very difficult and controversial. Planning a major airport is much like bathing a large angry elephant. It is very large, difficult, and you can definitely get hurt.
To get a perspective on the size of this airport, here is one square mile which is the size of Midway Airport, once the busiest airport in the world and still a very busy second airport for Chicago. Environmental regulations require very large distances from new major airports far exceeding the distances of existing airports.
It will likely be some time before the airport is actually built. It requires airlines to commit to using the airport, and there are few developers with the capacity to build the airport. And the existing major airlines in Chicago do not want competition.