Manchac Swamp Bridge
Coordinates30°18′11″N 90°24′21″W / 30.302946°N 90.405807°W / 30.302946; -90.405807
Carries I-55 / US 51
CrossesManchac Swamp
LocaleSt. John the Baptist Parish / Tangipahoa Parish, Louisiana, USA
Other name(s)I-55 Manchac Swamp Crossing
Maintained byLA DOTD
Characteristics
Total length22.8 miles (36.7 km)
Width312 feet (95 m)
History
Opened1979[1]
Location

The Manchac Swamp Bridge is a twin concrete trestle bridge near Manchac in the US state of Louisiana.[1] It 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.

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, and some claim it is the longest toll-free road bridge in the world.[4]

Opened in 1979,[1] with piles driven 250 feet (76 m) beneath the swamp, it cost $7 million per mile ($4.3 million/km) (equivalent to $22.9 million per mile ($14 million/km) in 2022[5]) to construct.[6]

A satellite view of the Manchac Swamp bridge (to the left) and the nearby Pontchartrain bridge


See also

References

  1. 1 2 3 Melaragno, Michele G. (1998). Preliminary Design of Bridges for Architects and Engineers. CRC Press. p. 377. ISBN 978-0-8247-0184-0. Retrieved June 20, 2010.
  2. "Manchac Swamp Bridge". Atlas Obscura. Retrieved May 2, 2019.
  3. "Manchac Swamp Bridge, one of the longest bridges in the world over water". www.dangerousroads.org. Retrieved March 7, 2022.
  4. "Longest Bridges in North America". WorldAtlas. August 1, 2017. Retrieved March 7, 2022.
  5. Johnston, Louis; Williamson, Samuel H. (2023). "What Was the U.S. GDP Then?". MeasuringWorth. Retrieved November 30, 2023. United States Gross Domestic Product deflator figures follow the Measuring Worth series.
  6. Loh, Jules (June 8, 1977). "Louisiana 'oasis' is cypress-paneled". The Tuscaloosa News. Tuscaloosa, Alabama. p. 6. Retrieved July 20, 2010.


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