Interstate 255

Interstate 255 (I-255) is a bypass route of Interstate 55 near St. Louis, Missouri and with Interstate 270, it forms a loop around the city. Even though St. Louis is in Missouri, a majority of the route runs through Illinois. It shares its southern terminus with 270 at the junction with Interstate 55, 270 goes to the west and 255 goes to the east. US 50 joins I-255 at Lemay Ferry Road. It crosses the Mississippi River on the Jefferson Barracks Bridge, enters Illinois, and then turns north. There is a junction with Interstate 64, where US-50 breaks off and goes east, and then further north there is a junction with Interstate 55 again, Interstate 70, and U.S. Route 40, all of which are all co-signed together. The next junction is another one with Interstate 270, and it is the northern terminus of Interstate 255. After that, it becomes Illinois Route 255.

Interstate 255 is 30.82 miles (49.60 km) in length.