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Interstate 270 Missouri / Illinois


Interstates 270 and 255 comprise the outer belt freeway system of the St. Louis metropolitan area. Interstate 270 begins at its interchange Interstates 55 and 255 south of St. Louis near Mehlville. From this location the highway loops around to the north and west, linking to Interstates 44, 64, and 70. Upon meeting Interstate 70, Interstate 270 begins curving to the east, bypassing the metro area to the north. At the Mississippi River, Interstate 270 crosses the Chain of the Rocks Bridge. Upon meeting Interstate 55/70 near Troy, Interstate 270 ends at a point approximately 15 miles to the east of the Mississippi River. By late 2001, the Interstate 255/Interstate 270 freeway in Missouri was dedicated the "American Veterans Memorial Highway".


The segment of Interstate 270 between Interstates 55 and 70 was originally signed as Interstate 244. To be more consistent, Interstate 244 was dropped in lieu of Interstate 270. The southern terminus of Interstate 270 is also the southern terminus of Interstate 255.

Other Facts

Regarding the Interstate 55/255/270 interchange in Mehlville, Rich Piehl writes that this interchange was a standard cloverleaf until about 15 years ago when the flyover ramps were built. At the same time the exits and entrances to Lindbergh Boulevard (just to the north of the interchange) were incorporated into the design to reduce the amount of traffic 'mixing' on the Interstate 55 mainline in a very short space. At the same time Lindbergh was changed from a diamond to a single point urban interchange (SPUI). Of note here is that since both Interstates 255 and 270 both run north (northeast and northwest respectively) from the centerpoint of the Interstate 55 overpass, they share a common zero (0) milemarker.

Brian Dowd writes about an interesting facet of Interstate 270's milemarkers:
"...I-270's mile markers reset when you cross the IL/MO border. Missouri counts it from mile 0 at Interstate 55 to mile 34 in St. Louis at the Mississippi River, but Illinois restarts its count at 0 and continues to 15 at I-55/I-70, however Interstate 70 continues to use this count (even though that is around mile 20 for I-70). Basically the I-270/Interstate 70 corridor in IL is mile marked as if it were a single roadway. I think IL probably leaves it alone because it would require renumbering all the mile markers and exit signs to add about 5 to each of them on I-70, and renumbering Interstate 270 from 0 to 15 to approx 34 to 49."

Missouri went through the Saint Louis region a year or so back and resigned the roads with newer style retroreflective sign panels. The sign erecting process began in the winter of 2000. Therefore many of the below photographs show the before and after results of the project.

Southern Terminus - Interstate 55 - Mehlville, Missouri
Perspective from Interstate 270 south
First glimpse of the Interstate 55 and U.S. Routes 61/67 interchange, 4.25 miles to the north via Interstate 270 southbound. Photo taken by Brian Dowd (06/02).
2.25 miles before the termini. This upcoming exits sign gives a clue that there really is no end to the freeway at the two termini. An exit for S.R. 231/Telegraph road is a couple miles after Interstate 55. Photo taken by Brian Dowd (06/02).
Notice this Interstate 55 panel explicitly calls this EXIT 1 A-B (even though it should read EXITS 1 A-B) versus the EXIT 1 in the next photo by Rich. Photo taken by Brian Dowd (06/02).
Interstate 55 overhead on Interstate 270 south at the Missouri 21 exit. Note that the right-hand panel has since been replaced. Photo taken by Rich Piehl (12/00).
Interstate 270 Ends signage. Notice that the transition to Interstate 255 is mentioned. Photo taken by Rich Piehl (12/00).
Interstate 55 and U.S. 61/67 sign bridge on Interstate 270 southbound. Photo taken by Rich Piehl (12/00).
Replacement of the sign-panel in the above photobox. Photo taken by Brian Dowd (06/02).
A collector-distributor lane takes traffic to both Interstate 55 and the U.S. 61/67 overlap. Meanwhile the travel lanes for Interstate 270 commit to Interstate 255. Photo taken by Brian Dowd (06/02).
The sign bridge in the background of the above photograph displays these guide signs for Exits 1A/B/C and the Interstate 270 collector/distributor roadway. Exit 1C serves the Mehlville area. Photo taken by Brian Dowd (06/02).
This photo shows the southern terminus of Interstate 270 (same signage in the above photograph). At this location, traffic continues east on Interstate 255 toward the Jefferson Barracks Bridge and the state of Illinois. Photo taken by Rich Piehl (12/00).
The interchange between Interstate 255/Interstate 270 and Interstate 55, which used to be total cloverleaf, now contains six directional ramps and two loop ramps. The traditional diamond ramps from Interstate 270 south to Interstate 55 south, Interstate 55 north to Interstate 255 east, Interstate 255 west to Interstate 55 north and Interstate 55 south to Interstate 270 north are accompanied by two directional flyovers from Interstate 55 north to Interstate 270 north and Interstate 55 south to Interstate 255 east while the ramps from Interstate 270 south to Interstate 55 north and Interstate 255 west to Interstate 55 south are loop ramps. Photo taken by Brian Dowd (06/02).
Traffic has two options for exiting onto U.S. Routes 61/67 off of the American Veterans Memorial Highway. First traffic can exit going from this ramp built into the Interstate 55 ramps to a southbound facing ramp to Lemay Ferry Road, or traffic can pass the Interstate 55 ramp system and exit onto a loop ramp which will put them facing northward to Lemay Ferry Rd just to the east of where the first ramp connects. The sign bridge in the background is for the traffic from Interstate 55 headed to Interstate 255 eastbound. Signage leading to the second exit to Lemay Ferry Road is also built into that ramp. Photo taken by Brian Dowd (06/02).
The overhead guide signs Pictured in the background of the above photograph. Photo taken by Brian Dowd (06/02).
Perspective from Interstate 255 west
Westbound Interstate 255 & U.S. Route 50 2.5 miles before the handover of the Interstate 270 designation from Interstate 255. U.S. 50 will leave Interstate 255 at the Lindbergh Blvd exit. Photo taken by Brian Dowd (06/02).
Guide Sign on westbound Interstate 255/U.S. Route 50 1.75 miles before Interstate 55. Odd that this sign (which appears to be a new retroreflective panel) refers to the Interstate 55 junction as EXIT 1 as it would be better qualified as EXITS 1 A-B. Photo taken by Brian Dowd (06/02).
MoDOT gets the exit number correct on this Interstate 55 guide sign. The Lindbergh Blvd sign technically should read U.S. 50 West/To U.S. 61/U.S. 67 since traffic does not get to U.S. Routes 61/67 for about one-third a mile north of the exit. Photo taken by Brian Dowd (06/02).
Another view of the sign bridge on Interstate 255 westbound at Exit 1D/Lindbergh Boulevard. Photo taken by Rich Piehl (12/00).
Upcoming exits sign, posted only three-fourths of a mile before the Interstate 55/270 junction. 274 miles to the south, is the Interstate 55 control city of Memphis. Only 103 miles away is Cape Girardeau. Photo taken by Brian Dowd (06/02).
Approaching the Interstate 55 junction, with the right-hand lane becoming an exit-only allocation for Exits 1A-B. Downtown Saint Louis sits just 11 miles north of this interchange. Photo taken by Brian Dowd (06/02).
The final two signs leading to northbound Interstate 270 from westbound Interstate 255. It should be said that the exit numbering for Interstate 55 on Interstate 255/Interstate 270 is a little odd. It does not matter which direction you approach the interchange, the first exit is Exit 1A, and the second is Exit 1B. Since both highways share a common milepost 0, this makes little sense. This violates the standard numbering convention where the suffixes of a numbered interchange should be in alphabetical order from milepost 0 eastward or northward. Therefore, the signage on Interstate 255 westbound is backwards. This is not the only location where this anomaly occurs, as Louisiana exit numbering conventions on Interstate 10 westbound in the Baton Rouge and New Orleans area is also backwards. Photos taken by Brian Dowd (06/02).
A second perspective of Interstate 255 westbound at Exit 1A for Interstate 55 north. Photo taken by Rich Piehl (12/00).
Interstate 270 Milepost Zero paddle at the Interstate 55/255 interchange. Photo taken by Rich Piehl (12/00).
Perspective from Interstate 55 north
This photograph shows a pretty typical panel on the arteries feeding into the beltway giving MoDOT's best effort to guide traffic that is attempting to get around the city. From Interstate 55, the fastest way to get to Illinois is to take Interstate 255 East. Similar signs are on Interstate 70 west of Missouri 370 (recommending drivers take Route 370 East to Interstate 270 East to Illinois), Eastbound Interstate 44 (recommending drivers take Interstate 270 South to Interstate 255 to Illinois) and on Westbound Interstate 270 (alerting drivers that Route 370 West is an alternate for Westbound Interstate 70 drivers heading to Wentzville and Kansas City). Photo taken by Brian Dowd (10/12/02).
This centerline panel is two miles before Interstate 270 and Interstate 255 and omits any mention of I-255. Brian Dowd believes that this sign is button copy and might predate the Interstate 255 designation (or could be a copy/replacement of a sign that did). Photo taken by Brian Dowd (10/12/02).
Five lanes of Interstate 55 northbound lanes just 1.50 miles before the Interstate 270/Interstate 255 interchange (Exit 196A-B). Photo taken by Brian Dowd (10/12/02).
0.75 milea before the splitoff for the American Veterans Memorial Highway, these EXIT ONLY lane assignment signs make their appearance. This is also a typical assembly for MoDOT in which each lane gets its own individual sign panel, instead of a single sign covering both directions like INDOT does on Southbound Interstate 65 at Interstate 465 on Indianspolis' Southside. Photo taken by Brian Dowd (10/12/02).
A second perspective of the Interstate 255/270 overheads on Interstate 55 north. Kansas City is 241 miles west via Interstate 270/70 while the city of Columbia (home of the University of Missouri) is 124 miles apart. Photo taken by Rich Piehl (12/07/00).
This centerline distance sign is 1/4 mile before the I-270/Interstate 255 splitoff. This give a good view of how the freeway looks. Interstate 55 was recently redone south of here all the way to Route M in Jefferson County. The project, which had a few stumbling blocks along the way, was deemed a success by MoDOT since the bond financed project came in on time and 2% under budget. Photo taken by Brian Dowd (10/12/02).
These signs attached to the Mattis Rd overpass in South St. Louis County are just past the 1/4 mile point before the beltway. Again, these signs are typical MoDOT assembly with separate signs for each lane, and the more condensed E series numbering in the 3di shields. Photo taken by Brian Dowd (10/12/02).
A second gander at the Exit 196A/B overheads as seen almost two years prior. Interstate 55 northbound continues with four through lanes beyond the Interstate 255/270 ramp departure. Photo taken by Rich Piehl (12/07/00).
At the gore for the Interstate 270/255 ramps. Even though Interstate 270 is marked here as going West, the directions are marked East-West to reduce confsion, as MoDOT consideres Interstate 270 as going Northbound (as shown by the first trailblazer) from Interstate 55 and Interstate 255 goes Eastbound. A closer inspection of the gore sign reveals that it is marked as Exit 196, the A/B suffix were added in 2000 by MoDOT when the signs were replaced at the request of the planning commission. All Interstate to Interstate interchanges had suffixes added to these stack ramps. This interchange design is kind of interesting. It is best described as a cloverstack. The ramps from Interstate 55 to Interstate 270/255 include stack flyovers, but the ramps from Interstate 255 and Interstate 270 include the legacy loop ramps for left movements. To the north is a single point urban interchange with U.S. Routes 50/61/67/Lindbergh Blvd which mixes with a collector distributor system between the exits. Photo taken by Brian Dowd (10/12/02).
Past the gore point the two respective ramps diverge. The two-lane flyover to Interstate 270 Northbound will connect with traffic heading to Interstate 270 Northbound from Southbound Interstate 55 before merging onto the freeway to the west suburbs. Traffic exiting onto Interstate 255 East will have the oppurtunity to exit onto U.S. Routes 61/67/Lemay Ferry Rd before merging with traffic coming from Interstate 55 Southbound and merging into Interstate 255 Eastbound. Also of note: The typical center West Interstate 270 [left arrow]/East Interstate 255 [right arrow] is replaced here with an Exit 196B gore sign. Photo taken by Brian Dowd (10/12/02).
Two years prio, the same Interstates 255 and 270 sign bridge on the ramp from Interstate 55 north. Interstate 255 connects with Interstate 55 again at Exit 25, with another 276 miles between the next meeting and the Windy City. Photo taken by Rich Piehl (12/07/00).
Perspective from Interstate 55 south
Advance signage for Interstate 255 and 270 at Exit 199 on Interstate 55 south. Photo taken by Rich Piehl (12/00).
Interstate 55 southbound approaching the junction with Interstate 255/270 and U.S. 50/61/67. Photo taken by Rich Piehl (12/00).
Interstate 255 east/Interstate 270 west sign bridge for Exits 196A/B on Interstate 55 southbound. This assembly is posted after the ramps depart from the mainline of Interstate 55. The Interstate 55 south to Interstate 255 east is a flyover. Photo taken by Brian Dowd (06/02).
Same sign bridge as Pictured in the above photograph. Photo taken by Rich Piehl (12/00).
Eastern Terminus - Interstate 55/Interstate 70 - Troy, Illinois
Perspective from Interstate 270
Eastbound Interstate 270 within the Interstate 55/70 interchange. The overlap of the two Interstates concludes at this Interstate, with Interstate 55 continuing northward to Chicago and Interstate 70 eastward to Indianapolis.Photo taken by Rich Piehl (4/01).
Merge of Interstate 270 eastbound with Interstate 70 eastbound. Interstate 70 will leave the state in 131 miles and reach Terre Haute, Indiana by 138. Photo taken by Rich Piehl (4/01).
Perspective from Interstate 55 south
Advance guide signage on Interstate 55 southbound for Exits 20B/A - Interstates 70/270. This interchange is a full cloverleaf with the exception of the ramp that merges westbound Interstate 70 traffic with southbound Interstate 55 traffic towards downtown. Through traffic for Kansas City and other western points stays on a more direct course via Interstate 270 north of the city of Saint Louis. It is actually shorter to bypass the city on Interstate 270 than to remain on Interstate 70 through the city. The Interstate 270 route between this interchange and Interstate 70 at Bridgeton, Missouri is about 30 miles. Interstate 70, as it dives into downtown Saint Louis from the north, is about 39 miles in length. Therefore traffic bypassing via Interstate 270 saves around nine miles of driving between here and their final destination. Photos taken by Brian Dowd (06/02).
Guide signage on Interstate 55 south at Exits 20B/A for Interstate 270 west and Interstate 70 east. The next southbound exit for Illinois 162 is located one and a half miles to the south. Exit 18 is the first off-ramp for the Interstate 55 south/70 west overlap. The two Interstate will stay together for approximately 21 miles through until downtown Saint Louis. Photo taken by Brian Dowd (06/02).
Night-time view of the overheads on Interstate 55 south at Exit 20B (same as in the above photograph). Photo taken by Jeff Royston (11/01).
Interstate 55 South at Interstate 270 west sign bridge (same as in the above photograph). Although Interstate 270 serves the northern reaches of the Saint Louis suburbs, the control city is displayed as Kansas City. Photo taken by Rich Piehl (4/01).
Perspective from Interstate 55 north/70 east
Interstate 55 northbound parts ways with Interstate 70 eastbound at Exit 20A. Exit 20B for Interstate 270 makes its debut to motorists on this sign bridge. A short distance to the north, can be found the loop ramp for the westbound beginning (Pictured in the next photograph). Photo taken by Rich Piehl (4/01).
Interstate 270 West/Exit 20B overhead on Interstate 55 north within the Interstates 55/70/270 interchange. 15 miles separate this ramp from the Mississippi River crossing of Interstate 270. Photo taken by Rich Piehl (4/01).
Perspective from Interstate 70 west
Westbound Interstate 70 two miles from Interstate 55 and Interstate 270 west. Photo taken 10/16/04.
Sign bridge on Interstate 70 westbound for Exits 15A/B - Interstate 55/270 west. Exit 15B for Interstate 55 north would logically make more sense if it were just Exit 15, since the ramp is located after Interstate 270 begins from Interstate 70. The logic behind this stems from the fact that it would be the first and only ramp of Interstate 270 within the 15 milepost zone, thus rendering the suffix unneeded. Photo taken 10/16/04.
Lane partitioning signage on Interstate 70 west, displaying the fact that Interstate 55 will overlap with Interstate 70. A problem exists with this signage though, in that there are no cardinal directions associated with either of the four displayed Interstate shields. Photos taken 10/16/04 and by Jeff Morrison (08/13/05).
Westbound Interstate 70 splits to the left as the mainline transitions to Interstate 270. As mentioned in the introduction, the mileage posts of Interstate 70 correlate with Interstate 270 westward through the Mississippi River. Interstate 55 enters the scene from the north, with Interstate 70 sharing pavement with Interstate 55 southward to downtown St. Louis. Photos taken 10/16/04 and by Jeff Morrison (08/13/05).
Traffic for Interstate 55 north must use the Interstate 270 travel lanes from Interstate 70 westbound. Interstate 55 distance to the state capital of Springfield is 73 miles with Chicago at 266. Interstate 270 is rural in nature as it travels westward to the Mississippi River and state of Missouri. Correlations can be drawn between the freeway and other rural stretches throughout the state of Illinois. The one exception in this comparison is that Interstate 270 carries more interchanges than any other typical stretch in the Land of Lincoln. Overall the freeway is four lanes in width, with a brief widening to six lanes in association with the Interstate 255/Illinois 255 interchange at Exit 7. After crossing into the Show Me State, the freeway changes landscapes drastically, with a standard six to eight lane width found throughout its routing. Photos taken by Brian Dowd (06/02) and Jeff Morrison (08/13/05).

Page Updated June 24, 2006.


State Missouri
Mileage 35.62
Cities St. Louis, Florissant, Ferguson, Bridgeton, Kirkwood
Junctions I-55, I-44, I-64, I-70, I-170
State Illinois
Mileage 14.97
Cities East St. Louis, Granite City
Junctions I-255, I-55, I-70
TOTAL 50.59
Source: December 31, 2016 Interstate Route Log and Finders List