Interstate 255 Missouri / Illinois

Interstate 255 Missouri
I-255 south Jefferson Barracks Bridge

I-255/U.S. 50 span the Mississippi River west from the American Bottoms area north of Columbia, Illinois to unincorporated Mehlville, Missouri. The tied arch bridges are named after the adjacent Jefferson Barracks National Cemetery. Photo by Joel Wade (04/16/05).


Forming the eastern third of a beltway around the metropolitan St. Louis, Interstate 255 provides a bypass route for I-55 and I-70 traffic. The freeway angles east from Mehlville, Missouri across the Jefferson Barracks Bridge over the Mississippi River to Columbia, Illinois. IL 3 ties into I-255 there as an expressway north from Waterloo. The two overlap north to Dupo before separating on respective courses north to Cahokia and northeast to Alorton.

Interstate 255 serves as a commuter route northward by St. Louis Downtown Airport (CPS) to I-64 at Caseyville and I-55/70 at Collinsville. U.S. 50 accompanies the freeway north from I-270 in Mehlville to I-64 east to O’Fallon. Beyond Collinsville, I-255 turns north to Pontoon Beach and a rural junction with I-270 and IL 255 north to Godfrey.

Route Information

  • North End – Pontoon Beach, IL

  • South End – Mehlville, MO

  • Total Mileage – 30.82


Missouri – 3.77

  • Cities – none

  • JunctionsI-55 I-70

Illinois – 27.05

  • Cities – Columbia, Centreville, East St. Louis, Collinsville

  • JunctionsI-55 I-70 I-270

Source: December 31, 2021 Interstate Route Log and Finders List

IL 3 north at I-255 - Columbia
IL 3 north at the three-wye interchange with Interstate 255 in the city of Columbia. Photo by Joel Wade (04/16/05).

Interstate 255 in Illinois is signed with north / south cardinal direction banners, while it is signed east / west in Missouri.


The recommended Interstate Marking for the St. Louis Urban Area approved by the American Association of State Highway Officials (AASHO) on November 10, 1958 outlined Interstate 255 along the Easterly route from I-55 at Mehlville, Illinois to I-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 the American Association of State Highway and Transportation (AASHTO) on June 25, 1974 was the renumbering of both I-244 and I-255 as an extended I-270.

St. Louis, MO - 1977

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 I-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 IL 255 freeway leading north to Alton.5

Illinois Route 255

Although Interstate 255 ends at I-270, the freeway continues north of I-270 as IL 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 freeway along IL 255 constructed was the 6.8 mile extension from I-255 north to IL 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 IL 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.

The Missouri Department of Transportation (MODOT) replaced signs throughout the Saint Louis region from winter 2000 to 2002 with newer style retroreflective sign panels. By late 2001, I-255 and I-270 in Missouri were dedicated the “American Veterans Memorial Highway”.

 Photo Guides

North End I-270 IL 255 – Pontoon Beach, Illinois

I-255 North at I-270 IL 255

I-255 north at I-270 - Pontoon Beach, IL

I-255 bends northwest through eastern reaches of Pontoon Beach to IL 162 and Interstate 270 at Exit 30. 05/24/18

I-255 north at I-270 - Pontoon Beach, IL

Traversing flat agricultural areas along I-255 north, one mile ahead of the transition to IL 255 at Interstate 270. 05/24/18

I-255 north at I-270 - Pontoon Beach, IL

Advancing north with four lanes, a lane drop occurs in one quarter mile for Exit 30 and Interstate 270. 05/24/18

I-255 north at I-270 - Pontoon Beach, IL

Exit 30 expands to two lanes for I-270 west to Granite City and the Chain of Rocks Bridge and I-270 east to Glen Carbon and Effingham. 05/24/18

I-255 north at I-270 - Pontoon Beach, IL

A two lane flyover connects with Interstate 270 west. The St. Louis bypass meets I-70 at Bridgeton in 22 miles. 05/24/18

IL 255 South at I-255 I-270

IL 255 south at I-255/270 - Edwardsville, IL

Crossing over Gateway Commerce Center Drive, IL 255 advances one mile south to the directional cloverleaf interchange with I-270 and I-255 south. 05/24/18

IL 255 south at I-255/270 - Edwardsville, IL

A number of distributor centers are located north of the upcoming exchange with Interstate 270. The exit numbering sequence for IL 255 concludes with I-270 assigned Exit 30 for I-255. 05/24/18

IL 255 south at I-255/270 - Edwardsville, IL

A collector distributor roadway partitions for I-270 west toward Kansas City and east toward Indianapolis as IL 255 transitions into I-255 south. 05/24/18

IL 255 south at I-255/270 - Edwardsville, IL

The ramp for Interstate 270 west to Bridgeton, Missouri departs from the c/d roadway at Exit 30. Kansas City lies 241 miles to the west via I-270 and I-70. 05/24/18

IL 255 south at I-255/270 - Edwardsville, IL

Interstate 270 converges with I-70 east near Troy in 7.8 miles. The capital city of Indiana is a 221 mile drive from IL 255 / I-255. 05/24/18

I-270 West at I-255 IL 255

I-270 west at I-255/IL 255 - Glen Carbon

Exit 7B departs from I-270 west for the IL 255 north. IL 255 extends 20.50 miles north from I-255 as a freeway to Alton and U.S. 67 north of Godfrey. 05/03/12

I-270 west at I-255/IL 255 - Glen Carbon

A loop ramp follows for Interstate 255 south to Caseyville, East St. Louis and Cahokia. 05/03/12

I-270 East at I-255 IL 255

I-270 east at I-255/IL 255 - Pontoon Beach, IL

Interstate 270 progresses 0.75 miles east from the cloverleaf interchange (Exit 6) with IL 111 in north Pontoon Beach to I-255 south and IL 255 north. 05/03/12

I-270 east at I-255/IL 255 - Pontoon Beach, IL

A collector distributor roadway separates from I-270 east at Exit 7 for I-255 south to Collinsville and IL 255 north to Alton. 05/03/12

I-270 east at I-255/IL 255 - Pontoon Beach, IL

Interstate 255 bypasses the east side of the St. Louis metro area to Mehlville and I-55 south to Memphis, Tennessee. 05/03/12

South End I-55 I-270 – Mehlville, Missouri

I-255 West at I-55 I-270

I-255 west at I-55/270 - Mehlville, MO

U.S. 50 (Lindbergh Boulevard) separates from Interstate 255 west to join the freeway with U.S. 61/67 through Mehlville. I-255 passes by South County Center mall to meet I-70 and I-270 over the ensuing mile Photo by Eric Stuve (08/18/18).

I-255 west at I-55/270 - Mehlville, MO

A loop ramp from U.S. 61 (Lemay Ferry Road) adds a westbound auxiliary lane to Interstate 255 for Exit 1B and I-55 north 12 miles to Downtown St. Louis. 05/03/12

I-255 west at I-55/270 - Mehlville, MO

Entering the cloverstack interchange (Exits 1B/A) with Interstate 55 on I-255 west. Crossing the River Des Peres Drainage Channel, I-55 north enters the Patch neighborhood of St. Louis in five miles. 05/03/12

I-255 west at I-55/270 - Mehlville, MO

Interstate 55 weaves through the south suburbs to 22 miles to Festus. Photo by Eric Stuve (08/18/18).

I-270 East at I-55 I-255

I-270 south at I-55/255 - Concord, MO

Interstate 270 advances east from Missouri Route 21 through unincorporated Concord to I-255. MODOT typically signs the ends of Interstates and other major freeways with this style of sign. Photo by Eric Stuve (09/22/15).

I-270 south at I-55/255 - Concord, MO

A collector distributor roadway separates movements from the I-270/255 eastbound main line for I-55 south to Festus, I-55 north to St. Louis and the nearby commercial stretch along U.S. 61/67 (Lemay Ferry Road). Photo by H.B. Elkins (05/13/11).

I-270 south at I-55/255 - Concord, MO

Three lanes continue east onto Interstate 255 toward the Jefferson Barracks Bridge and Columbia, Illinois. The c/d roadway at Exit 1A partitions for I-55 south to Memphis and north to Lemay and the Poplar Street Bridge across the Mississippi River. Photo by H.B. Elkins (05/13/11).

I-270 east at I-55/255 - 2002

Replaced button copy guide signs at the loop ramp for Interstate 55 north. Now unnumbered, this ramp was formerly Exit 1B. Photo by Brian Dowd (06/02).

I-55 North at I-255 I-270

I-55 north at I-255/270 - Mehlville, MO

Interstate 55 ultimately expands to six northbound lanes leading into the multi level interchange (Exits 196A/B) with I-255/270 at Mehlville. 12/20/09

I-55 north at I-255/270 - Mehlville, MO

Interstate 55 runs just west of adjacent U.S. 61/67 (Lemay Ferry Road) to Exit 196 for I-270 north to Bridgeton and I-255 east to Collinsville, Illinois. 12/20/09

I-55 north at I-255/270 - Mehlville, MO

Passing under Mattis Road, traffic headed for the St. Louis beltway separate from Interstate 55 north in one quarter mile. I-270 north to I-70 west leads 241 miles to Kansas City. 12/20/09

I-55 north at I-255/270 - Mehlville, MO

I-55 advances north with four through lanes toward St. Louis as Exit 196 parts ways for the St. Louis beltway. Ramps for I-270 west and I-255 east were previously assigned as Exits 196A/B respectively. This change was made at the request of the planning commission, but subsequently changed back. 12/20/09

I-55 north at I-255/270 - Mehlville, MO

I-270 encircles the west suburbs north through Maryland Heights and the north suburbs east to the Chain of Rocks Bridge. I-255 combines with U.S. 50 nearby to cross the Jefferson Barracks Bridge into Monroe County, Illinois. Photo by Brian Dowd (10/12/02).

I-55 South at I-255 I-270

I-55 south at I-255/270 - Affton, MO

A c/d roadway to I-255/270 and U.S. 61-67-50 (Lindbergh Boulevard) separates from I-55 south two miles beyond Reavis Barracks Road at Affton. 04/13/13

I-55 south at I-255/270 - Affton, MO

Continuing across Gravois Creek, I-55 makes an S-curve between the city of Green River and unincorporated Mehlville to Exit 197 for Lindbergh Boulevard, I-255 east and I-270 west. Photo by Eric Stuve (05/19/04).

I-55 south at I-255/270 - Affton, MO

U.S. 50 converges with I-255 east from Lindbergh in Mehlville, joining the freeway ahead of the Jefferson Barracks Bridge to Columbia, Illinois. U.S. 61/67 (Lindbergh Boulevard) parallel I-270 northwest to Sappington, Sunset Hills and Kirkwood. Photo by Eric Stuve (05/19/04).

I-55 south at I-255/270 - Affton, MO

The c/d roadway and flyover for Interstate 255 east measures 1.282 miles in length from the Exit 197 gore point. Photo by Eric Stuve (05/19/04).

I-55 south at I-255 - 2002

Ramps from I-55 combine before merging onto I-255 east just prior to Exit 1C for U.S. 61/67 (Lemay Ferry Road). Exit 1C was previously Exit 1B. Photo taken by Brian Dowd (06/02).


  1. MISO (Missouri Interstate Route Numbering), Interstate system route numbering web site, Stephen Summers.
  2. July 26, 1988 – A ceremony on I-255 north of Granite City marked the completion of the Interstate loop around St. Louis, Construction on the Missouri side began in 1962, and was finished by 1969. The 38-mile Missouri loop was divided into I-270, 244 and 255. In 1974, officials considered naming the whole thing after John F. Kennedy, then decided to designate it as 270 on the Missouri side, 255 in Illinois. [Facebook update]. Retrieved from
  3. “Jefferson Barracks Bridge Opens…Crowd Braves Harsh Wind To Watch Span’s Dedication.” St. Louis Post-Dispatch (MO), December 4, 1990.
  4. “I-255 Rim Means Loop is Finished – For Now.” St. Louis Post-Dispatch (MO), July 31, 1988.
  5. “One-Mile Piece of I-255 Will Open Today.” St. Louis Post-Dispatch (MO), March 15, 1988.
  6. “Metro East area is in the loop – 21-mile, four-lane freeway will arc from I-270 and link to U.S. 67 near Godfrey.” St. Louis Post-Dispatch (MO), July 14, 2010.
  7. “Illinois 255 extends its reach to Godfrey.” Edwardsville Intelligencer (IL), August 26, 2008.
  8. “Illinois 255 opens to Godfrey ‘Y’.” The Telegraph (Alton, IL), November 22, 2012.
  9. “Routes 67 and 255 Come Together.” Alton Daily (IL), July 19, 2013.

Page updated July 17, 2021.