Manchac Swamp Bridge
bridge in Louisiana, US
The Manchac Swamp Bridge is a twin concrete trestle bridge near Manchac in the U.S. state of Louisiana. 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), 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.
Opened in 1979, with piles driven 250 feet (76 m) beneath the swamp, it cost $7 million per mile ($4.3 million/km), equivalent to $24.3 million per mile ($15 million/km) in 2024, to construct.
2023 Manchac Swamp Bridge Car Crash
The 2023 Manchac Swamp Bridge Car Crash occurred on October 23, 2023, on Interstate 55 in St. John the Baptist Parish, Louisiana. The incident was primarily caused by a combination of heavy fog and drifting smoke from nearby marsh fires, a phenomenon known as superfog. The crash took place on the elevated section of I-55, which spans from Ponchatoula to LaPlace over the swamplands below. During the crash, one vehicle fell into the water and partially sank, while over 100 motorists were left stranded until rescue services could reach the area. The collision involved 168 vehicles, resulting in 8 fatalities and 63 injuries.
This brief starts where responsible research should: with the source description of “Manchac Swamp Bridge” as bridge in Louisiana, US. Everything that follows is an evidence route, not borrowed authority.
Why this record matters
The subject matters to the places & architecture register because the source frames it as bridge in Louisiana, US. Its deeper value depends on whether names, dates, institutions and citations support that framing.
Place names and jurisdictional language are key evidence: both can reveal earlier catalogue descriptions and overlooked record series. The source revision retrieved here is dated Jul 17, 2026. The linked authority identifier is Q1888744. Authority coordinates are 30.303, -90.406. 2 of 2 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank. The first chronological checks are 1979, 2024 and 2023.
Architectural summaries often privilege surviving fabric and can understate demolished phases, contested use or displaced communities. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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Three-step research path
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Questions for further research
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This entry incorporates text from “Manchac Swamp Bridge” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.