The Adeline Jay Geo-Karis Illinois Beach State Park (IBSP) consists of 6.5 miles of Lake Michigan shoreline in the city of Zion, Lake County, Illinois. IBSP is bordered by the Wisconsin state line to the north, Lake Michigan to the east, the town of Zion to the west, and the Johns-Manville National Priorities List (NPL) hazardous waste site to the south. IBSP encompasses 4,160 acres of shoreline. Available recreational activities include camping, swimming, fishing, hiking, bicycling, and picnicking. Facilities within and near the park boundaries include the North Point Marina, a 244-unit campground, two major public swimming areas, several inland fishing ponds, a visitor center, the Commonwealth Edison Power Plant, and the Illinois Beach Resort and Conference Center. Besides seasonal tourism, visitors are drawn to the park by special park events, including the In-Campground Camper Show in May and the National Jet Ski Championships in July.

The state considers the park a unique natural resource, one with the only remaining Lake Michigan beach ridge shoreline in the state. Glacial advance and retreat created the area and left dunes, swales, marshes, and a variety of wildlife and vegetation. Before it became a state park, the military used the area for training. In 1948, Illinois acquired the first parcels of what is now IBSP.

In late 1997, pieces of transite pipe, siding, and roofing materials suspected of containing asbestos were found scattered along the beach. In February 1998, the Illinois Department of Natural Resources (IDNR) collected two bulk samples of the material and found they contained asbestos fibers. Following this discovery, IDNR began an investigation to determine the extent and possible source of asbestos contamination at the park.