Discover the Longest Bridge in Louisiana – A 24-Mile Behemoth!

Updated: August 12, 2023
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Key Points:

  • The Lake Pontchartrain Causeway, which runs between the two New Orleans suburbs of Metairie and Mandeville, is 23.9 miles long and is built entirely over water.
  • The Causeway is actually two bridges built parallel to each other in 1956 and 1969; it was built to accommodate marine traffic with wide spans and a drawbridge.
  • At one point, you can’t see either shore, so there is a turnaround spot for people who lose their nerve, but commuters are grateful for the shortcut into the city.
Bridge Infographic for the Lake Pontchartrain Causeway in New Orleans, Louisiana.
This causeway is still the longest bridge in the world that runs continuously over water.

Bridges, though often taken for granted, are necessary, practical, and important to our way of life. They allow people to travel across large bodies of water and other unnavigable areas. Some of the world’s bridges are amazingly long. This is typically the case when they span large bays or lakes. With a large percentage of Louisiana comprised of water, four of the five longest bridges in the United States are located in the state! But of these four, which is the longest bridge in Louisiana? Read on to find out!

What Is the Longest Bridge in Louisiana?

Lake Pontchartrain Causeway
The Lake Pontchartrain Causeway was the world’s longest bridge over water from 1969 to 2011.

©Mark Runde/

The longest bridge in Louisiana is the Lake Pontchartrain Causeway. It is an impressive 23.9 miles long. Many local residents simply call it “The Causeway.” As the name implies, the bridge crosses Lake Pontchartrain in southeastern Louisiana.

The Lake Pontchartrain Causeway is technically two bridges that run parallel to one another. One bridge is for northbound vehicles, while the other is for southbound cars. The southern end of the bridge is in Metairie, directly adjacent to New Orleans. The northern end is in Mandeville, which residents fondly refer to as the North Shore. Both of these towns are considered suburbs of New Orleans.

Not only is this the longest bridge in Louisiana, but it was the world’s longest bridge over water from 1969 to 2011. The Jiaozhou Bay Bridge in China broke this record when it opened in 2011.

However, Guinness World Records specified two categories for bridges over water. Lake Pontchartrain Causeway is the longest bridge over water (continuous), while the Jiaozhou Bay Bridge is the longest bridge over water (aggregate). While the length of the causeway is entirely over water, significant parts of the record-breaking bridge in China are situated over land.

Some people actually find driving on this bridge overwhelming because of its length. Eight miles into the bridge, drivers can’t see land on either side. In rare cases, police officers have had to pick up panicked drivers and take them to the end of the bridge themselves!

Where is the Longest Bridge in Louisiana Located on a Map?

The longest bridge in Louisiana is the Lake Pontchartrain Causeway, a 23.9-mile double bridge that connects the town of Mandeville to New Orleans. The bridge spans Lake Pontchartrain and is so long that land can’t be seen from its middle point.

History of the Longest Bridge in Louisiana

The initial purpose of a bridge spanning Lake Pontchartrain was to make it easier to drive between the north and south shores of the lake without having to go all the way around it.

Before The Causeway existed, Bernard de Marigny, the founder of Mandeville, started a ferry service across the lake that operated into the mid-1930s. There was also talk of creating artificial islands linked by multiple bridges.

Ernest de Loëb came up with the idea to build the modern bridge in 1948. The Louisiana Bridge Company then formed to construct this bridge.

Originally, this was a single two-lane bridge. Workers completed construction in 1956. The original bridge is now the southbound branch. Workers finished the northbound bridge 14 years later, in 1969. The purpose of the parallel bridge was to alleviate excessive congestion on the initial bridge.

Since its opening, it has been a toll bridge. Tolls are used to fund maintenance and safety improvements on The Causeway itself.

The bridge has made life easier for several North Shore residents by reducing the commute time into New Orleans by approximately 50 minutes. The American Society of Civil Engineers designated the Lake Pontchartrain Causeway as a National Historic Civil Engineering Landmark in 2013.

Structure of the Longest Bridge in Louisiana

The southbound bridge consists of 2,246 spans, or decks, and the northbound bridge consists of 1,506 spans. Each of the spans consists of monolithically cast concrete girders, rails, and decks. They have precast pile bents as support, with more piles in regions with longer spans.

The bridge was constructed in a way that accommodated marine navigation. The majority of the spans of the Lake Pontchartrain Causeway are approximately 10 feet above the water level.

The drawbridge at the 16-mile marker, eight miles from the North Shore, gives marine vessels 45 feet of clearance. The fixed high-rise at the eight-mile marker provides 50 feet of clearance, and there are three low rises that provide 25 feet of clearance.

There are six segmented shoulders along each bridge for safety, to prevent vehicles from driving off the bridge. In 1964, barges caused damage to the bridge, creating a gap. As a result, a bus fell from the bridge into the lake, killing six people. Ever since then, safety bolsters have been a priority.

What Are the Other Longest Bridges in Louisiana?

The I-10 Bonnet Carré Spillway Bridge is 11 miles long and connects New Orleans and Baton Rouge.

©Ray Devlin from New Orleans (for now), USA / CC BY 2.0 – License

The following bridges in Louisiana make the list of the longest five bridges in the country:

  • I-10 Bonnet Carré Spillway Bridge: 11 miles long, connecting New Orleans and Baton Rouge
  • Atchafalaya Basin Bridge: 18 miles long, connecting Baton Rouge and Lafayette
  • Manchac Swamp Bridge: 23 miles long, crossing the Manchac Swamp

Animals Under the Longest Bridge in Louisiana

American alligators make their home in Lake Pontchartrain.

© Larson

Lake Pontchartrain is home to a very diverse assortment of wildlife. In addition to all of the animals, there are many single-celled organisms, such as protozoans and diatoms. Fungi have also lived in the lake, including lichens. There are over 5,000 total organisms that we know to inhabit this area under the Lake Pontchartrain Causeway!

Many species of fish and eels swim through these waters. These include the American eel, silver perch, spotted sea trout, freshwater drum, white bass, great barracuda, bluegill, crappie, and multiple sunfish species.

As far as amphibians go, there are many different species of frogs, toads, and salamanders here. These include the American toad, southern toad, northern cricket frog, Cuban tree frog, American bullfrog, marbled salamander, and mole salamander. Reptiles include the American alligator and prairie lizard.

In the water basin, you may see a West Indian manatee. Land animals surrounding the basin include swamp rabbits, Virginia opossums, nine-banded armadillos, American beavers, and several species of squirrel.

Additionally, many bird species are present in this area, like various species of cuckoo, woodpeckers, owls, and doves.

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