The Blanchette Memorial Bridge is a pair of twin cantilever bridges carrying Interstate 70 across the Missouri River between St. Louis County and St. Charles County, Missouri, opened in 1959. At the bridge's crossing, the Missouri River reaches an average depth of about 45 feet. Handling an average of 165,000 vehicle transits per day, it is the area's busiest bridge. Construction of the first interstate highway project under provisions of the Federal Aid Highway Act of 1956 started west of the bridge's present location. A sign commemorating the site of the nation's first interstate project stands next to Interstate 70 just east of the Missouri Route 94/First Capitol Drive overpass.