I-55 within Illinois carries heavy traffic, with an average of more than 20,000 vehicles per day for most of its length. Significant portions of I-55 contain six lanes (three lanes in each direction) and are heavily used by commuters. I-55 in Illinois begins in
East St. Louis on the
Poplar Street Bridge over the
Mississippi River at the Missouri state line and runs southwest to northeast through the state, ending in
Chicago at
US 41 (
Lake Shore Drive). Along the way, it goes through four metropolitan areas in the state: the Illinois portion of the
St. Louis metropolitan area, the
Springfield metropolitan area, the
Bloomington–
Normal metropolitan area, and the
Chicago metropolitan area (also known as
Chicagoland).
East St. Louis to Springfield I-55 enters Illinois on the Poplar Street Bridge from Missouri,
running concurrently with
I-64 and
US 40. The highway meets
Illinois Route 3 (IL 3) at a series of complex interchanges. IL 3 joins I-55/I-64/US 40 for approximately . Still in East St. Louis, I-64 and IL 3 leave I-55/US 40, while the current routing of
I-70 joins the pair. The three routes continue north-northeast, intersecting the southern terminus of
IL 203 near
Granite City,
IL 111 near
Fairmont Park,
I-255 and
IL 157 in
Collinsville, and
IL 159 in
Maryville. Approximately after the IL 159 interchange, US 40 leaves I-55/I-70. After an interchange with
IL 162 in
Troy, I-70 heads east toward
Effingham. At the same interchange,
I-270 intersects I-55 and ends. On its way further north, I-55 intersects
IL 143 near
Edwardsville,
IL 140 in
Hamel,
IL 4 south of
Livingston, local roads that connect to Livingston and
Staunton, and
IL 138 near
White City. About further north, I-55 intersects
IL 16 at a larger interchange to the west of
Litchfield. It then goes another before meeting the eastern terminus of
IL 108 to the east of
Carlinville. Continuing along, it meets the southern and northern termini of
IL 48 and
IL 127 west of
Raymond, local roads to
Farmersville and
Divernon,
IL 104 near
Auburn, and two local roads to
Glenarm and
Chatham. At the East Lake Drive interchange, I-55 crosses over Lake Springfield into
Springfield proper.
Springfield to Bloomington I-55 enters Springfield at an interchange with Toronto Road. About further north, it meets
I-72 and
US 36 to form a concurrency that skirts the southern and eastern edges of the city. At the same interchange, it meets the southern end of
I-55 Business (I-55 Bus.). I-55/I-72/US 36 has two interchanges while on the concurrency: Stevenson Drive/East Lake Drive and
IL 29. north, I-72 and US 36 head east toward
Decatur and
Champaign. At this interchange, I-55 intersects
IL 97, which leads to downtown Springfield. I-55 then crosses the western terminus of
IL 54 (old
US 54). further north, it meets the northern terminus of I-55 Bus., effectively leaving Springfield. From Springfield to Chicago, I-55 follows a northeast–southwest path. In
Williamsville, it meets
IL 123 near its eastern terminus. It crosses two local roads, providing access to
Elkhart and
Broadwell before heading north into
Lincoln. In Lincoln, I-55 meets the southern terminus of the second
I-55 Bus. It then heads due north to intersect
IL 10 and the northern terminus of
IL 121. north, it meets the southern terminus of
I-155. At this interchange, it heads due east to meet the northern terminus of I-55 Bus. before resuming its northeasterly–southwesterly course through northern Illinois. I-55 meets an interchange with a local road leading to
Atlanta,
US 136 in
McLean, and another local road near
Shirley before entering the
Bloomington–
Normal area.
Bloomington to Joliet Once entering Bloomington, I-55 forms a complex interchange with the southern terminus of the final
I-55 Bus. to the north and
I-74/
US 51 to the east. At this interchange, I-74 and US 51 overlap I-55 around the western edge of the cities. The highway has one interchange at
US 150 and
IL 9. I-74 splits from I-55/US 51 further north to head toward
Peoria and the
Moline–
Rock Island area. Less than east, US 51 splits from I-55 to follow
I-39 toward the
LaSalle–
Peru area and toward
Rockford. Before leaving Bloomington–Normal, I-55 has two more interchanges with
US 51 Business (US 51 Bus.) and I-55 Bus. From Bloomington to Joliet, I-55 continues its northeasterly–southwesterly trek while skirting the western edges of various towns along the way. It meets local roads connecting
Towanda and
Lexington,
US 24 in
Chenoa,
IL 116 and
IL 23 in
Pontiac, a local road to
Odell,
IL 17 and
IL 47 in
Dwight, and
IL 53 in
Gardner. I-55 starts showing hints of entering the Chicago metropolitan area after the IL 53 interchange. It passes through Forest Preserve areas between Gardner and
Joliet. After IL 53, I-55 intersects a local road and
IL 113 near
Braidwood and meets a partial interchange at
IL 129; drivers who want to access IL 129 from southbound I-55 can connect via IL 113. Continuing north, I-55 intersects local roads in industrial areas before entering
Channahon. It has two interchanges with Bluff Road and
US 6. north, it meets
I-80, which forms the boundary of Channahon and Joliet.
Joliet to Chicago From I-80, I-55 enters the Joliet area by means of
Shorewood, with a diverging diamond interchange (DDI) at
IL 59 and a full interchange with
US 52. It enters Joliet proper with an interchange at
US 30. It then connects with
IL 126 near
Plainfield, forming a partial interchange, then enters the
Bolingbrook–
Romeoville area, meeting interchanges at Weber Road and IL 53 again. , heading southwest On the border of Romeoville and
Lemont, I-55 meets
I-355 and a former routing of
US 66 at a large, complex interchange. It then meets Lemont Road near Lemont, Cass Avenue and
IL 83 near
Darien, and County Line Road in
Burr Ridge. It enters another large, complex interchange with
I-294 and another former routing of US 66 in
Indian Head Park. Further east, it meets a large interchange with
US 12/
US 20/
US 45 south of
Countryside. About northeast, it meets a rather large interchange with
IL 171 and an interchange with
IL 43, both near
Summit. After the IL 43 interchange, I-55 enters Chicago. From IL 43, I-55 meets various city streets (also including one interchange with
IL 50, which leads to
Midway International Airport) before reaching
I-90/
I-94 (also known locally as the
Dan Ryan Expressway) approximately west of its terminus. North of I-90/I-94, I-55 intersects various city streets at partial interchanges before reaching its national northern terminus at
US 41 (
Lake Shore Drive). ==History==