Interstate 270 (Missouri–Illinois)
Interstate 270 (I-270) makes up a large portion of the outer belt freeway in Greater St. Louis. The counterclockwise terminus of I-270 is at the junction with I-55 and I-255 in Mehlville, Missouri; the clockwise terminus of the freeway is at the junction with I-55 and I-70 north of Troy, Illinois. The entire stretch of I-270 is 50.59 miles (81.42 km).
Interstate 270 | |||||||
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I-270 highlighted in red | |||||||
Route information | |||||||
Auxiliary route of I-70 | |||||||
Maintained by IDOT and MoDOT | |||||||
Length | 50.59 mi (81.42 km) | ||||||
Existed | 1956–present | ||||||
NHS | Entire route | ||||||
Major junctions | |||||||
South end | I-55 / I-255 in Mehlville, MO | ||||||
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East end | I-55 / I-70 near Troy, IL | ||||||
Location | |||||||
Country | United States | ||||||
Counties | MO: St. Louis, City of St. Louis IL: Madison | ||||||
Highway system | |||||||
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I-270 between I-70 and I-55 was formerly designated I-244, a western bypass of St. Louis, Missouri. It was originally proposed by Missouri as I-144, but the road was a beltway (or part of one), so the American Association of State Highway and Transportation Officials (AASHTO) assigned it the number I-244. By the late 1970s, the entire beltway (including today's I-255) was integrated as a part of I-270 for consistency. However, the politicians in Illinois started planning their supplemental freeway system in the mid-1970s, and a five-mile (8.0 km) section of Corridor 413 was included into the Interstate Highway System in April 1978. This caused a potential place of confusion in Pontoon Beach, Illinois, where I-270 would have intersected itself, and eventually the Illinois Department of Transportation (IDOT) decided on the I-255 numbering in 1980 (but not before considering renumbering an eight-mile (13 km) section to I-870).