The Greater Chicago Industrial Zone (often referred to simply as "The Zone") is a Human city on Earth, located on the continent of North America near Lake Michigan. An outgrowth of the modern-day American city of Chicago, the Zone is a vast urban sprawl covering large parts of the "former" states of Illinois, Wisconsin, and Indiana. The Great Lakes Spaceport is located nearby. Before the Battle of Earth, Chicago had a population of 54 million people. The Zone was the hometown of Avery Johnson.