U.S. Route 66 in Illinois

U.S. Route 66
Will Rogers Highway Main Street of America
Path of Route 66 in dark green
Route information
Maintained by IDOT
Length:	301 mi (484 km)
Existed:	November 11, 1926 (1926-11-11) – June 25, 1974 (1974-06-25)
Major junctions
West end:	US 66 at the Mississippi River towards St. Louis, MO
	I-64 / IL 3 in East St. Louis I-70 / I-270 in Troy I-80 in Joliet I-90 / I-94 in Chicago
East end:	US 41 in Chicago
Highway system
United States Numbered Highway System List Special Divided Replaced Illinois State Highway System Interstate U.S. State Tollways ← IL 64 US 67 →

U.S. Route 66 (US 66, Route 66) was a United States Numbered Highway in Illinois that connected St. Louis, Missouri, and Chicago, Illinois. The highway had previously been Illinois Route 4 (IL 4) and the road has now been largely replaced with Interstate 55 (I-55). Parts of the road still carry traffic and six separate portions of the roadbed have been listed on the National Register of Historic Places.

When US 66—first known as the Main Street of America and later dubbed the Mother Road by novelist John Steinbeck in 1939—was designated on November 11, 1926, the original path used mostly pre-existing roads. That was intentional, to minimize any needed construction and to get the entire path of the route open to traffic as soon as possible. In fact, because Illinois had already paved most of the roads that would comprise US 66, Illinois was the first of the eight states through which the route ran to have its segment of US 66 completed at a time when much of Route 66 was still a gravel-and-dirt road.

In Illinois and the Midwest in general, the construction of US 66 was important to the economies of small, rural towns, which saw a burst of activity when the road finally passed through. However, those communities in Illinois were already profiting from a paved highway that preceded Route 66 by a few years. In 1916, the Federal Aid Post Road Act, known as the Shackleford Bill, passed Congress and appropriated $75 million to be distributed to the states over the next five years. Funding was provided on an ongoing basis, over the period of five years, and the law made the federal government an active partner in road building for the first time. Five roads in Illinois were designated to receive federal money under the legislation; they were: the National Old Trails Road (National Road, present-day US 40), Lincoln Highway, Dixie Highway, the road from Chicago to Waukegan, and the road from Chicago to East St. Louis, including portions of IL 4, which was the actual predecessor to US 66 in Illinois.