The Lake Pontchartrain Causeway is actually two separate bridges that run parallel to each other but are different lengths. As of 2014, it remains the longest bridge in the world.
Bernard de Marigny, founder of Mandeville, La., the bridge's northern terminus, started a ferry service across the lake that operated from the early 1800s until the 1920s. After a plan to build bridges between man-made islands was dropped in the 1930s, a new project was developed, and construction on the Lake Pontchartrain Causeway began in 1948. The first part of the bridge was completed in 1956. A second parallel bridge was completed in 1969 and is 15 meters longer than the first.
For decades Louisiana could boast that Lake Pontchartrain Causeway, which spans 23.79 miles, held the Guinness Record for the longest bridge over water in the world. However, in 2011, China almost claimed the record with Jiaozhou Bay Bridge, which is 26.4 miles long. After some debate, Guinness updated its records to reflect that the Lake Pontchartrain Causeway holds the record for the longest continuous bridge over water because the bridge in China includes portions that cross dry land and pass through undersea tunnels. The parts that cross water only total 16.1 miles.