I-270
Get started	Mehlville
End	Troy
Length	50 mi
Length	81 km
Route 1 → St. Louis / Chicago / Memphis2 Tesson Ferry Road 3 Gravois Road 5 → St. Louis / Springfield 7 Big Bend Road 8 Dougherty Ferry Road 9 Manchester Road 12 → St. Louis / Wentzville 13 Ladue Road 14 Olive Boulevard 16 → St. Charles 17 Dorsett Road 20 → St. Louis / Kansas City 20C St Charles Rock Road 22 → St. Charles 23 James S. McDonnell Boulevard 25 Lindbergh Boulevard 26 → St. Louis Airport 26B Hanley Road 27 New Florissant Road 28 Elizabeth Avenue 29 Florissant Avenue 30 New Halls Ferry Road 30A Old Halls Ferry Road 31 Alton 32 Bellefontaine Road 33 Lilac Avenue 34 Riverview Drive New Chain of Rocks Bridge 3 Granite City / Alton 4 Old Alton Road 6 Pontoon Beach 7 → St. Louis Beltway 9 Glen Carbon 12 Edwardsville 15 → Chicago / Indianapolis

Interstate 270 or I -270 is an Interstate Highway in the US states of Missouri and Illinois. The highway forms a partial ring road around the west and north sides of St. Louis. Along with Interstate 255, I-270 forms a complete ring road around the city. I-270 is 81 kilometers long.

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Travel directions

I-270 with frontage roads.

Interstate 270 on the north side of St. Louis.

The New Chain of Rocks Bridge over the Mississippi River.

Interstate 270 begins at a major interchange with I-55 and I-255 in Mehlville. Interstate 55 comes from Memphis and continues into downtown St. Louis, while Interstate 255 forms the eastern beltway. I-270 then proceeds northwest in 2×4 lanes and serves the western suburbs of St. Louis. At Crestwood one crosses Interstate 44, the highway from Oklahoma City, Tulsa and Springfield to St. Louis. After that, 2×4 lanes are also available while driving through the wooded suburbs. At Creve Coeur you cross the Interstate 64, which runs from the western suburb of Chesterfield toward downtown, and on to Louisville, Kentucky.

I-270 then already runs due north and even has 2×5 lanes. A little further on, at Maryland Heights, one crosses Interstate 70, which comes from Kansas City and heads toward downtown and Indianapolis. Through traffic on I-70 goes here via I-270, as that route rejoins I-70 at the end, is shorter, and avoids downtown St. Louis. Interstate 270 also turns east here, passing the St. Louis airport. State Route 370 ends at Hazelwood, a short bypass of the suburb of St. Charles. I-270 has 2×4 lanes here. Interstate 170. begins at the suburb of Florissant, a short north-south link through the front row of suburbs west of St. Louis. After this, I-270 narrows to 2×3 lanes. One then passes through the suburban area north of St. Louis. At Glasgow Village, the New Chain of Rocks Bridge follows over the Mississippi River, which has 2×2 lanes here.

One then reaches the state of Illinois. One passes by Granite City and intersects Interstate 255, St. Louis’ eastern beltway. To the north, State Route 255 continues as a highway. I-270 then continues for a few more miles to Troy, where the highway ends at an interchange where Interstate 70 continues straight toward Indianapolis and Interstate 55 heads north.

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History

Interstate 270 is one of the older highways in Missouri. The first section opened in 1962 in the northwestern suburbs. In 1969 the St. Louis bypass on the Missouri side was completed. Formerly, the western bypass, between I-55 and I-70, was known as Interstate 244. In 1966, the New Chain of Rocks Bridge opened over the Mississippi River.

I-270 proved its worth during the great floods of 1993, when the bridge was the only intact bridge across the Mississippi to Keokuk in Iowa, 300 kilometers upstream. In 2010, the interchange with Dorsett Road was transformed into a diverging diamond interchange, one of the first in the United States.

Widening

In 2012-2013, I-270 between I-44 and Manchester Road was widened from 2×4 to 2×5 lanes over 5 miles. In December 2012, the 5th lane opened to the north, on October 18, 2013, the 5th lane opened to the south.

Opening history

From	Unpleasant	Length	Opening
Exit 20	Exit 27	11 km	1962
Exit 27	exit 33	10 km	1963
Exit 5	Exit 9	6 km	1964
Exit 9	Exit 14	8 km	1966
exit 33	Exit 3 (IL)	7 km	1966
Exit 14	Exit 20	10 km	1967
Exit 4	Exit 5	2 km	1968
Exit 1	Exit 4	6 km	1969

Future

Except for 2.5 miles, I-270 has 6 or more lanes everywhere. The only narrow section left is north of St. Louis, between Bellefontaine Road and the Illinois border. It is planned to eventually replace the New Chain of Rocks Bridge over the Mississippi River with a wider bridge. On the Illinois side, the bridge over the Mississippi River side channel was replaced between October 2011 and mid-2014.

Traffic intensities

Interstate 270 is a busy highway. There are 145,000 vehicles between I-55 and I-44 and 163,000 vehicles on to I-64. There are 181,000 vehicles up to I-70 and 132,000 vehicles along the north side. 60,000 vehicles cross the Mississippi River every day.

Lane Configuration

The interchange between I-270 and SR-370 in Bridgeton.

From	Unpleasant	Lanes	Comments
exit 0	exit 12	2×5
exit 12	Exit 14	2×4
Exit 14	Exit 23	2×5
Exit 23	Exit 26	2×4
Exit 26	exit 33	2×3
exit 33	Exit 15	2×2	Exit 15 at Illinois