Editing Interstate 255 (section)

==History==
[[File:St Louis, Missouri 1955 Yellow Book.jpg|thumb|left|The Yellow Book plan in Greater St. Louis]]
I-255 route was proposed from I-55/I-244 near [[Green Park, Missouri|Green Park]] to I-55/70 west of [[Cahokia Mounds]] near the intersection with [[Illinois Route 111|IL&nbsp;111]] when plans surfaced in the 1950s Yellow Book.<ref>{{cite map|url=http://www.lib.utexas.edu/maps/world_cities/st.louis.jpg|title=St. Louis, Missouri|scale=1:500,000}}</ref> It was originally designed to be a four lane highway but was changed to six lanes.<ref>{{cite news |work = Alton Telegraph |date = April 29, 1977 }}{{Full citation needed|date=March 2022}}</ref>

Since that routing was to go through the American Bottoms, archaeological investigations had to be conducted prior to any construction, which would later become known as the FAI&nbsp;270 Series.<ref>{{Cite web |title=FAI-270 Series: American Bottom Archaeology |url=https://www.itarp.uiuc.edu/pubs/fai270_series.html |url-status=dead |archive-url=https://web.archive.org/web/20110720085217/http://www.itarp.uiuc.edu/pubs/fai270_series.html |archive-date=July 20, 2011 |access-date=March 12, 2022 |publisher=Illinois Transportation Archaeological Research Program}}</ref> When Cahokia Mounds was designated in the federal register, an alternative alignment for I-255 from I-64 to I-55/70 was selected.<ref>{{cite news |work = Edwardsville Intelligencer |date = July 9, 1973 }}{{Full citation needed|date=March 2022}}</ref> This delayed construction of I-255 until the late 1970s, making it the last Interstate Highway in metropolitan St. Louis to be built.

Both the western (I-270) and eastern (I-255) portions of the Interstate loop around St. Louis were originally designated as I-270.<ref>{{Illinois road map |year=1968 |access-date=November 24, 2022}}</ref> However, the route that Illinois selected ("Corridor&nbsp;413"<ref>{{Cite web |last=Dees |first=Dan C. |date=November 1, 1974 |title=Federal-aid Freeway System - Supplemental Freeways |url=http://www.midwestroads.com/illinois/il%20supp%20fwy.pdf |access-date=March 12, 2022 |via=MidwestRoads.com |publisher=[[Illinois Department of Transportation]]}}</ref>) included an interchange in Pontoon Beach between the new beltway (running north and south parallel to the Mississippi River) and the existing beltway (running east and west to a terminus at I-55/I-70). As such, two intersecting Interstate Highways would have carried the same route number.<ref name="ReferenceA">IDOT FAI-270/FAP 413 Draft EIS Volume 1, 1983</ref> As such, the [[Illinois Department of Transportation]] (IDOT) concluded a different route number would be necessary for the eastern leg of the beltway. While I-870 was initially considered,<ref>[https://web.archive.org/web/20120314012318/http://img706.imageshack.us/img706/3282/is270eis1.jpg I-270/870 proposed routes]{{Full citation needed|date=March 2022}}</ref> informal use of I-255 in contemporary local media coverage led to its widespread adoption. By 1980, IDOT announced that the eastern portion of the St. Louis beltway was to be designated as I-255.