Illinois 390 is the newest state highway designation in Illinois, applied to a stretch of tollway known for decades as the "Elgin-O'Hare Expressway." The road wasn't a tollway until about the last decade, when the Illlinois State Toll Highway Authority took over the roadway to extend it. Despite the name "Elgin-O'Hare Expressway," the small fragment of expressway never reached Elgin or O'Hare, though it provided a freeway option for a piece of the route between those two points. With the new expansion eastward, currently underway, the expressway will indeed connect to the western access point to O'Hare Airport. At this point, Illinois 390 extends from its unchanged western terminus of US Route 20 near Hanover Park, east to Illinois 83 at Bensenville.
Illinois 390's eastern end is currently at Illinois 83, where all traffic is forced off of the tollway. The extension of this tollway eastward continues, and the highway will eventually access O'Hare and a new highway wrapping around the airport.