Introduction

Opened in October 1962, the route in St. Louis has seen several changes in nearly 40 years, especially on the Missouri side.  Since the mid 60s, 270 has absorbed I-244 and for a period of five to ten years, the current routing of I-255 from I-55 to I-55/70.  It has been widened several times during the same period of time, I-170 was built.  Three different sets of exit numbers have been used on the Missouri side of the river, while nothing has changed once you cross the Chain of Rocks Bridge.

The completion of the New Chain of Rocks Bridge in September 1966 marked the completion of the original route of 270, which went from I-70 in Champ, MO to I-55 in Troy, IL.  Other than the construction of MO 370, I-170, and 255, plus the occasional bridge/sign replacement projects, little has changed on the original route.

The biggest changes came on the route that was once I-244.  Population growth in West St. Louis and St. Charles Counties forced MoDOT to widen the highway several times since the early-1980s.  Seven major interchanges have (or currently) underground reconstruction projects, including all the interchanges with other interstate highways.

At one point, the entire beltway was dubbed 270.  However, IDOT apparently had plans of their own and the newer, eastern bypass from I-55 in South St. Louis County to I-270 near Mitchell, IL was designated I-255.  The eastern bypass was built during the 1980s and was completed on December 3, 1990 when the eastbound JB Bridge span was opened to traffic.