Interstate 55 South Manchac Swamp Bridge Whole Part 1

The Manchac Swamp Bridge is a twin concrete trestle bridge near Manchac in the US state of Louisiana.[1] With a total length of 22.80 miles (36.69 km),[2][3] it is one of the longest bridges in the world over water and is the longest bridge on the Interstate Highway System. Some claim it is the longest toll-free road bridge in the world.[4] The bridge carries Interstate 55 and U.S. Route 51 over the Manchac Swamp in Louisiana and represents a third of the highway's approximately 66 miles (106 km) in Louisiana. Opening in 1979,[1] its piles were driven 250 feet (76 m) beneath the swamp and with the cost of the span being $7 million per mile ($4.3 million/km) (equivalent to $21.4 million per mile ($13 million/km) in 2021[5]) to complete.[6]