The recommended Interstate Marking for the St. Louis Urban Area approved by AASHO on November 10, 1958 outlined Interstate 255 along the Easterly route from I-55 at Mehlville, Illinois to Interstates 55 & 70 at Collinsville. I-270 north from Mehville to I-70 at Bridgeton was numbered as Interstate 244, with I-270 designated on the North Beltway only.1 Construction on the I-255 portion in Missouri got underway in 1962. It was completed in 1969.2
Changes made to the St. Louis area numbered route system in 1974 included the relocation of U.S. 50 over what was previously designated as U.S. 50 Bypass, from Sunset Hills, Missouri to Fairview Heights, Illinois. The elimination of U.S. 50 Bypass coincided with the relocation of the U.S. 50 mainline onto I-255 from Illinois 3 south of Cahokia to Lindbergh Boulevard at Mehlville. Also approved by AASHTO on June 25, 1974 was the renumbering of both Interstates 244 and 255 as an extended I-270.
1977 Illinois Official Highway Map showing the small portion of Interstate 255 opened at the time as I-270.
Illinois and Missouri opted to restore Interstate 255 along the beltway east from south St. Louis County to Glen Carbon in 1979. Twin tier arched bridges, the Jefferson Barracks Bridge carrying I-255 & U.S. 50 westbound across the Mississippi River opened initially with one span in July 1984. The eventual eastbound bridge opened to traffic on December 3, 1990.3
Interstate 255 was completed from the Jefferson Barracks Bridge northeast to Interstates 55 & 70 in 1986. During that time, state officials successfully convinced the federal government to lengthen the route another six miles to meet Interstate 270 northeast of Pontoon Beach.4 This extension was completed on March 15, 1988 and it included provisions for the eventual Illinois 255 freeway leading north to Alton.5
Although Interstate 255 ends at Interstate 270, the freeway continues north of Interstate 270 as Illinois 255. Planning for the route commenced in 1988 as I-255 was nearing completion. However the Alton Bypass was not part of federal highway plans, so funding for it would come at the state level.6
The first portion of the IL 255 freeway constructed was the 6.8-mile extension from I-255 north to Illinois 143 (Edwardsville Road). It opened in October 1998 at a cost of $88.7-million. Estimations for the continuation of the freeway north to Godfrey ballooned to $200 million, leading to skepticism that it would ever be built. Lobbying by the Committee For Completion of Highway 255 ushered the public behind the effort, leading to the May 1999 allocation of $180 million for IL 255 by Governor George Ryan.6
Work was slow to begin, and the 7.6-mile $78.1-million stretch between IL 143 and Fosterburg Road in Alton opened in October 2006.6 Construction progressed from there on a $25.1-million 2.75 mile segment to Seminary Road. It was completed in August 22, 2008.7
The next stage of construction kicked off in May 2010 on a $21.9-million project involving 3.4 miles of new roadway to U.S. 67 in Godfrey.6 The freeway opened between Seminary Road and Humbert Road at Godfrey on October 26, 2012 and from Humbert Road to Illinois 111 (Montclaire Avenue on November 21, 2012.7 This left final work on the "Godfrey Y", the wye interchange with U.S. 67 leading northwest to Jerseyville, which was fully opened by mid-July 2013.8 The entire IL 255 corridor is envisioned as the southern leg of a planned four-lane route along U.S. 67 linking the St. Louis area with the Quad Cities.7
Since the freeway was constructed with state funds, it is not a candidate for Interstate status. However, that also depends upon whether an Interstate-grade facility is constructed along U.S. 67, as some Western Illinois politicians have wanted for years.
MODOT replaced signs throughout the Saint Louis region from winter 2000 to 2002 with newer style retroreflective sign panels. By late 2001, the Interstates 255 and 270 in Missouri was dedicated the “American Veterans Memorial Highway”.