The Daniel Boone Bridge are two twin cantilever bridge

Cantilever bridge

A cantilever bridge is a bridge built using cantilevers, structures that project horizontally into space, supported on only one end. For small footbridges, the cantilevers may be simple beams; however, large cantilever bridges designed to handle road or rail traffic use trusses built from...

s carrying Interstate 64

Interstate 64

Interstate 64 is an Interstate Highway in the Midwestern and Southeastern United States. Its western terminus is at I-70, U.S. 40, and U.S. 61 in Wentzville, Missouri. Its eastern terminus is at an interchange with I-264 and I-664 at Bowers Hill in Chesapeake, Virginia. As I-64 is concurrent with...

, U.S. Route 40

U.S. Route 40

U.S. Route 40 is an east–west United States highway. As with most routes whose numbers end in a zero, U.S. 40 once traversed the entire United States. It is one of the original 1920s U.S. Highways, and its first termini were San Francisco, California, and Atlantic City, New Jersey...

 and U.S. Route 61

U.S. Route 61

U.S. Route 61 is the official designation for a United States highway that runs from New Orleans, Louisiana, to the city of Wyoming, Minnesota. The highway generally follows the course of the Mississippi River, and is designated the Great River Road for much of its route. As of 2004, the highway's...

 across the Missouri River

Missouri River

The Missouri River flows through the central United States, and is a tributary of the Mississippi River. It is the longest river in North America and drains the third largest area, though only the thirteenth largest by discharge. The Missouri's watershed encompasses most of the American Great...

 between St. Louis County and St. Charles County

Saint Charles County, Missouri

As of 2000, there were 283,883 people, 101,663 households, and 77,060 families residing in the county. The population density was 507 people per square mile . There were 105,514 housing units at an average density of 73 persons/km²...

, Missouri

Missouri

Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...

.

On December 10, 2004, the Missouri Highways and Transportation Commission approved the design location of a third span, to be built upstream (to the west) of the two current spans. This new span will carry eastbound traffic, while the current eastbound span will carry westbound traffic. Funding was approved in July 2011 and construction is expected to begin in 2013. The original bridge is deteriorating quickly, and will be demolished once the new westbound bridge is completed.

1932 Bridge

The original bridge was built in 1932. It carries three narrow lanes with little, to no shoulders. As the AADT is increasing, the need for a wider bridge with standard lanes and shoulders is increasing. As the bridge was built nearly 70 years ago, it is eligible for the NRHP list. As of 2011, the bridge will be replaced and removed when the new bridge is built.