The Lake Pontchartrain Causeway, which consists of two parallel bridges, holds the distinction as the longest over-water highway in the world by total length. The 24-mile long bridge spans 1/1000th of the earth’s circumference on its trek between Metairie and Mandeville, Louisiana. The causeway is a marvelous engineering project and a wonder to behold as you drive over it with the blue of the water and the blue of the sky merging in the distance ahead of you. The bridge is 24-miles long, and consists of two parallel decks 80-feet apart each outfitted with two lanes of traffic. The decks are supported by more than 9,000 pilings and joined by seven turnaround zones for emergency vehicles. Each weekday over 42,000 cars cross Lake Pontchartrain on the longest bridge in the world, The Lake Pontchartrain Causeway.

The Causeway is one of the oldest prestressed concrete bridges in the United States. The idea of a bridge spanning Lake Pontchartrain dates back to the early 19th Century and Bernard de Mandeville, the founder of Mandeville. He started a ferry service that continued to operate into the mid-1930s. The original design featured two separate drawbridges, each eight mile from shore. The $29 million 24 mile project opened four months ahead of schedule to much fanfare. It took 200 engineers and workmen to complete the job. To build the bridge, engineers loaded pieces of the bridge onto barges and transported them to the construction points on the lake. The Causeway is supported by more than 9,500 hollow pilings, approximately 55 inches in diameter. Since its opening in 1956, traffic has grown from 3,000 vehicles per day to 3,500 vehicles during a peak hour. The August 30, 1956 opening date culminated with the assembly of 2,243 piles, each supporting a 33 foot wide 56 foot section of roadway. The parallel span to the 1956 bridge began during September of 1967. The $26 million project completed in 25 months with only two construction related deaths reported. This bridgework resulted in new bascules, widening of the navigational channel to 125 feet, and the replacement of southern drawbridge with a ship channel. On May 10, 1969, the causeway opened to traffic.