Interstate 55 in Illinois

I-55 within Illinois carries heavy traffic, with an average of more than 20,000 vehicles per day for most of its length.[3] Significant portions of I-55 contain six lanes (three lanes in each direction) and are heavily used by commuters.[4] I-55 in Illinois begins in East St. Louis on the Poplar Street Bridge over the Mississippi River at the Missouri–Illinois state line[4] 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).[4]

I-55 enters the Chicago metro area as the Stevenson Expressway and provides easy access to downtown Chicago via both the I-90/I-94 (Dan Ryan Expressway) interchange and US 41 (Lake Shore Drive) at the northern terminus of I-55, near Cermak Road and the lakefront.

I-55 in Illinois is the fourth road to connect St. Louis and Chicago. The first was the Pontiac Trail in 1915. This was largely improved and paved as the new Illinois Route 4 (IL 4) by 1924.[5] In 1926, IL 4 was designated as the route of the new U.S 66, and a new section of US 66 was built to bypass slower sections of IL 4 south of Springfield by 1930. Through the 1950s US 66 was continually widened, straightened, and improved to handle its growing traffic, until its entire length was four lanes wide by 1957.[6]

The roots of I-55 could be traced back to the need of a national highway system.[7] President Dwight D. Eisenhower saw the need of a national network of highways that would help with the mobilization of the army. He had been impressed with the autobahn he saw in Germany during World War II. In 1956 he signed the Federal Aid Highway Act into existence.[7] Although the act provided for a highway replacing Route 66, it was spared destruction for a while because of it being more modern than other routes at the time.[7] Illinois would build its first new Interstate highways on other routes such as I-80, I-57, and I-70, before turning its attention once again to the St. Louis-to-Chicago route.

However, during the 1970s, Route 66 was finally replaced by I-55 as the fourth St. Louis-to-Chicago highway, serving most of the same communities along the way as the original Pontiac Trail. It was built in sections across Illinois, often on the original Route 66 roadbed. A common construction tactic where Route 66 was already four lanes wide, was to build new southbound lanes for I-55 west of the original road, then rebuild the original southbound lanes of US 66 to be the new northbound lanes for I-55, leaving the original northbound lanes of old US 66 as a two-way frontage road.[7] One can find many signs posted for Historic US 66, especially where it deviates from I-55.

The earliest stretch of I-55 was a portion of US 66 which had already been built as a freeway between Gardner and I-294 (Tri-State Tollway) in Indian Head Park, and which was added to the Interstate system by simply erecting new signs in 1960.[8] Later portions of the highway were built in the 1960s between East St. Louis and Hamel, as bypasses of Springfield and Bloomington-Normal.[9] The rest of the road was completed in the 1970s.

The Stevenson Expressway near Countryside, heading southwest

The Stevenson Expressway opened on October 24, 1964 as the Southwest Expressway. It was renamed after Adlai Stevenson,[10] the former governor of Illinois, on September 1, 1965, a month and a half after his death. The Stevenson's original termini were US 66 in DuPage County to the west, and the Dan Ryan Expressway to the east.

In 1999–2000, the expressway was completely rebuilt from Central Avenue north to Lake Shore Drive, including the ramps to the Dan Ryan. The Illinois Department of Transportation (IDOT) was criticized at the time for not adding a fourth lane in each direction to the highway.[11]

In 2017, the Illinois General Assembly voted to rename approximately 70 miles (110 km) of I-55 from the Tri-State Tollway (I-294) to Pontiac in honor of Barack Obama.[12][13]

Governor Bruce Rauner, in early 2016, made a proposal to explore expanding the Stevenson Expressway portion of I-55 by adding an additional lane in each direction to ease congestion. Under his proposal, toll lanes would be constructed and operated through a potential private-public partnership.[21]

Wikimedia Commons has media related to Interstate 55 in Illinois.

• Stevenson Expressway Timeline at the Chicago Public Library
• Historic, Current & Average Travel Times For The Stevenson Expressway

Interstate 55
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