Illinois Route 255
| Alton Bypass | ||||
IL 255 highlighted in red | ||||
| Route information | ||||
| Maintained by IDOT | ||||
| Length | 23.3 mi (37.5 km) | |||
| Existed | October 1998–present | |||
| Major junctions | ||||
| South end | I-255 / I-270 in Pontoon Beach | |||
| North end | US 67 in Godfrey | |||
| Location | ||||
| Country | United States | |||
| State | Illinois | |||
| Counties | Madison | |||
| Highway system | ||||
| ||||
Illinois Route 255 (IL 255), also referred to as the Alton Bypass, is a northwesterly extension of Interstate 255 (I-255) in southwestern Illinois in the St. Louis metropolitan area. IL 255 starts at I-270 in Pontoon Beach and ends at U.S. Route 67 (US 67) in Godfrey, at a total length of approximately 23.3 miles (37.5 km). It was constructed in four segments opening from 1998 to 2012 at a total cost of $165.2 million.