I-64 enters Illinois
running concurrently with
I–55 and
U.S. Route 40 (US 40) over the
Mississippi River on the
Poplar Street Bridge. After splitting from these highways in
East St. Louis, I-64 turns southeasterly and proceeds through
St. Clair County towards the
Belleville area traveling through the eastern/southeastern St. Louis suburbs of
Caseyville,
Fairview Heights,
O'Fallon, and
Shiloh. In Shiloh, the Interstate skirts the northern edge of
Scott Air Force Base and
MidAmerica St. Louis Airport and provides access to
Mascoutah and
Lebanon via
Illinois Route 4 (IL 4). A new interchange at Rieder Road was completed in September 2017 to create better access to Scott Air Force Base. As part of the new interchange, a third lane in each direction, a wide left shoulder to accommodate a future fourth lane in each direction, and a center
Jersey barrier was added from west of Air Mobility Drive/
IL 158 to Rieder Road. At the St. Clair–
Clinton county line, the Interstate passes the exurb of
New Baden, after which it crosses the southern boundary of Clinton County and leaves the St. Louis metropolitan area. It then traverses a rural part of Illinois through
Washington and
Jefferson counties, which has no adjacent cities or major intersections passing; it reaches the city of
Mount Vernon in Jefferson County, where it has a short concurrency with
I-57. Mount Vernon is the only major city and intersection served by I-64 in Illinois outside of the St. Louis metropolitan area. Past Mount Vernon, the Interstate enters another rural stretch through parts of Jefferson,
Wayne, and
White counties before crossing the
Wabash River into Indiana. ==History==