Interstate 55 (I-55) is a major Interstate Highway in the central United States. As with most primary Interstates that end in a five, it is a major cross-country, north–south route, connecting the Gulf of Mexico to the Great Lakes. The highway travels from LaPlace, Louisiana, at I-10 to Chicago, Illinois, at U.S. Route 41 (US 41), at McCormick Place. The major cities that I-55 connects to are (from south to north); Jackson, Mississippi; Memphis, Tennessee; St. Louis, Missouri; and Chicago, Illinois.
The section of I-55 between Chicago and St. Louis was built as an alternate route for U.S. Route 66 (US 66). The Interstate crosses the Mississippi River twice: once at Memphis and again at St. Louis.
History
When it was realized that a national highway system was needed, the Federal-Aid Highway Act of 1956 provided for a highway replacing the old US 66 which I-55 filled. I-55 was originally constructed in the 1960s, to extend a section of US 66 between I-294 and Gardner which had been converted into a freeway and had Interstate signage installed in 1960. During the rest of the 1960s, I-55 was built in portions throughout Illinois, eventually connecting St. Louis to Chicago, where it became the fourth direct route between them. As it goes southward, most of the Interstate was purpose-built during the 1960s and 1970s. The entire length was completed in 1979.