The MacArthur Bridge was the second bridge to carry Route 66 across the Mississippi River - from 1929 to 1935.  It's a unique, double-deck bridge designed to carry both vehicular traffic and railroad traffic.  The top deck was for automobiles and the bottom deck was for the railroad.

Originally named the Saint Louis Municipal Bridge, it opened to vehicular traffic in 1917. Since it didn't require a toll, it was dubbed the "Free Bridge" to locals. In 1931, the lower deck was opened and began to carry trains across the river. In 1932, a small toll was added. In 1942, the bridge was renamed the General Douglas MacArthur Bridge.

This bridge carried Route 66 from 1929 until 1935. From 1936 to 1955, the route over the bridge was designated as "City US-66."

By 1981, the upper deck was closed. Most of the upper deck has been removed.