Interstate 255

Interstate 255
I-255 highlighted in red
Route information
Auxiliary route of I-55
Maintained by IDOT and MoDOT
Length	30.82 mi[1] (49.60 km)
Existed	1986–present
History	Completed by 1989[2]
NHS	Entire route
Major junctions
West end	I-55 / I-270 in Mehlville, MO
Major intersections	US 50 / US 61 / US 67 in Mehlville, MO I-64 / US 50 in Washington Park, IL I-55 / I-70 / US 40 in Collinsville, IL
North end	I-270 / IL 255 in Pontoon Beach, IL
Location
Country	United States
Counties	MO: St. Louis IL: Monroe, St. Clair, Madison
Highway system
Interstate Highway System Main Auxiliary Suffixed Business Future
Missouri State Highway System Interstate US State Supplemental
Illinois State Highway System Interstate US State Tollways Scenic
← Route 254 MO → Route 265 ← IL 251 IL → IL 255

Interstate 255 (I-255) is a bypass route of I-55 in Greater St. Louis. Along with I-270, it forms a loop around the central portion of the bi-state metro area; a majority of I-255 is located on the Illinois half. It shares its southern terminus with I-270 at the junction with I-55; I-270 and I-255 go to the west and east, respectively. U.S. Route 50 (US 50) joins I-255 at Lemay Ferry Road. It crosses the Mississippi River on the Jefferson Barracks Bridge, enters Illinois, and then turns northeast. There is a junction with I-64, where US 50 breaks off and goes east, and then further north there is a junction with I-55 again, I-70, and US 40, all of which are all cosigned together. The next junction is another one with I-270, which is the northern terminus of I-255. After that, the limited-access freeway continues on as Illinois Route 255 (IL 255). I-255 is 30.82 miles (49.60 km) in length.