Interstate 270 | |||||||
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Route information | |||||||
Maintained by IDOT and MoDOT | |||||||
Length: | 50.59 mi (81.42 km) | ||||||
Existed: | 1956 – present | ||||||
Major junctions | |||||||
CCW end: | I-55 / I-255 in Mehlville, MO | ||||||
I-44 / US 50 / Route 366 in Sunset Hills, MO I-64 / US 40 / US 61 in Town and Country, MO I-70 in Bridgeton, MO US 67 in Hazelwood, MO I-170 in Hazelwood, MO I-255 / IL 255 near Pontoon Beach, IL |
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CW end: | I-55 / I-70 near Troy, IL | ||||||
Highway system | |||||||
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Interstate 270 (I-270) makes up a large portion of the outer belt freeway in the St. Louis, Missouri metropolitan area. The counterclockwise terminus of I-270 is at the junction with I-55 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).
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).
The section of I-270 on the Missouri side was completed by June 1964, while the section that was I-244 was completed by November 1968. The section from Illinois Route 3 (IL 3) to I-55 in Illinois was finished by May 1965.