Drivers crossing the Mississippi River between St. Louis County, Missouri, and Madison County, Illinois, are about to get a lot more room to breathe. The new westbound Interstate 270 bridge at Chain of Rocks is set to open Monday, Nov. 16, completing a years-long replacement of the aging 1966 span that carried traffic with narrow shoulders and frequent maintenance headaches.
The opening marks the centerpiece of a combined $531.6 million investment, according to the Illinois Department of Transportation, which breaks down to $496.2 million for the bridges themselves and a companion $35.4 million project rebuilding the Riverview Drive interchange. The eastbound span already opened in late 2024, and now its westbound twin is following roughly two years later. KSDK, which first reported the project's price tag and November opening date, pegged the overall cost at $532 million in its coverage of the KSDK story on the ribbon-cutting.
The old bridge, built in 1966, had just two lanes in each direction and shoulders so narrow that a broken-down car left almost nowhere to pull off safely. The new bridges will initially carry two lanes in each direction as well, the Illinois Department of Transportation says, with three lanes in each direction planned once additional construction wraps up in a future season. That timeline tracks with a report from St. Louis Public Radio, which said both the eastbound and westbound bridges are expected to have three lanes open by next summer.
A Bridge Built for More Than 50,000 Vehicles a Day
MoDOT Director Ed Hassinger said the span will carry serious traffic volume once it's fully open. “This bridge will carry in excess of 50,000 vehicles a day between Missouri and Illinois,” Hassinger said, per the Illinois Department of Transportation's announcement.
Other traffic estimates for the crossing vary depending on the source and date. A 2023 report from Transport Topics put daily traffic at 51,000 vehicles, 20% of them trucks, and noted that figure dwarfs a 1975 projection of just 19,800 vehicles per day. A separate 2024 report from the St. Louis Regional Freightway described the existing bridge as serving nearly 45,000 vehicles daily, also with a 20% truck share. The discrepancy reflects differing counts rather than a single agreed-upon number.
Coordinating Across State Lines on Future Capacity
Illinois and Missouri transportation officials say they're not done thinking about capacity on this stretch of I-270. The two states continue to coordinate on long-term plans to add a third lane in each direction extending as far east as Illinois 157, according to the same Illinois Department of Transportation release.
That kind of cross-border planning fits into a broader regional freight picture. The St. Louis Regional Freightway reported in February 2024 that the Chain of Rocks replacement was being led by the Illinois Department of Transportation in partnership with the Missouri Department of Transportation, and that the finished structure was designed as a dual roadway featuring three traffic lanes and 10-foot shoulders on each side. The freight agency also noted that nearly $2.7 billion in projects on its priority list were under construction or partially funded at the time, underscoring how much regional infrastructure spending has been moving in parallel.
Freight Stakes Loom Large Over the Crossing
The crossing matters well beyond daily commuters. It serves truck drivers hauling goods through the St. Louis region, and those truck trips can stretch hundreds of miles, according to facts tied to the KSDK report on the project.
Gia Biagi said the project aims to add capacity, reduce congestion, and help travelers arrive on time, and added that the crossing has an impact not just locally but across the Midwest and the United States, per the same KSDK reporting. Transport Topics had earlier reported, in June 2023, that completion of the bridge replacement project was expected by Dec. 31, 2026 — putting the November 16 opening just ahead of that original target.
For now, the practical difference for drivers will be immediate: shoulders wide enough to actually pull over on, instead of the roughly one-foot buffer the old Chain of Rocks bridge offered in the event of a crash. Officials cut the ribbon on the new Interstate 270 bridge and Riverview Boulevard interchange project this month, formally marking the end of a construction effort that linked northern St. Louis County with Madison County, Illinois, through one of the busiest river crossings in the region.
