Manchac Swamp Bridge: The Longest Bridge over a Swamp in the World

The Manchac Swamp Bridge is an iconic structure that spans over the Manchac Swamp in Louisiana, United States. With a length of 22.80 miles (36.69 kilometers), it is the longest bridge over a swamp in the world. The bridge is a part of the Interstate 55 highway that connects New Orleans and Hammond, Louisiana.

History and Construction

The Manchac Swamp Bridge was constructed as a part of the upgrade of the Interstate 55 highway in the 1970s. The original highway was a narrow two-lane road that passed through the swampy terrain of Manchac. Due to the frequent flooding and poor road conditions, the state authorities decided to construct a modern highway that would be elevated above the swamp.

The construction of the bridge was a challenging task due to the unstable nature of the swampy terrain. The engineers had to design a bridge that would be able to withstand the weight of heavy vehicles and the dynamic forces of wind and water. The construction of the bridge took four years and cost $7 million.

Design and Features

The Manchac Swamp Bridge is a concrete trestle bridge that consists of 1,884 spans. The bridge is supported by 9,500 pilings that are driven deep into the swampy soil. The bridge has a maximum height of 155 feet (47 meters) above the swamp, which allows large boats and barges to pass underneath it.

The bridge has two lanes in each direction and is designed to handle heavy traffic. The bridge is also equipped with an advanced drainage system that prevents water from accumulating on the roadway. The bridge has a life expectancy of 100 years and is regularly maintained by the state authorities.

Tourism and Attractions

The Manchac Swamp Bridge is a popular tourist attraction in Louisiana. The bridge provides a breathtaking view of the swamp and the surrounding landscape. The bridge is also a popular spot for fishing and boating. Visitors can rent a boat and explore the swamp or fish for catfish, bass, and other species.

The Manchac Swamp is also home to a variety of wildlife, including alligators, turtles, snakes, and birds. Visitors can take a guided swamp tour and learn about the ecology and history of the swamp.

The bridge is also famous for its ghost stories. According to local legends, the bridge is haunted by the ghosts of people who died in the swamp. Visitors can take a haunted swamp tour and hear the eerie stories of the ghostly sightings.


The Manchac Swamp Bridge is not just a transportation infrastructure but also a marvel of engineering and a tourist attraction. The bridge has become a symbol of Louisiana’s rich culture and history. The bridge provides a unique perspective of the swamp and its wildlife, and visitors can experience the thrill of crossing the longest bridge over a swamp in the world.