Lake Pontchartrain in the context of St. Tammany Parish, Louisiana

The Lake Pontchartrain Causeway (French: Chaussée du lac Pontchartrain), also known simply as The Causeway, is a fixed link composed of two parallel bridges crossing Lake Pontchartrain in southeastern Louisiana, United States. The longer of the two bridges is 23.83 miles (38.35 km) long. The southern terminus of the causeway is in Metairie, Louisiana, and the northern terminus is in Mandeville, Louisiana. Both are in the New Orleans metropolitan area.

The Lake Pontchartrain Causeway holds the Guinness World Record for longest continuous span over water in the world. It previously was listed as longest bridge over water in the world; in 2011, in response to the opening of the Qingdao Jiaozhou Bay Bridge in China, Guinness World Records created two categories for bridges over water: Lake Pontchartrain Causeway then became the longest bridge over water (continuous), while the Jiaozhou Bay Bridge became the longest bridge over water (aggregate).

Slidell /slaɪˈdɛl/ is a city on the northeast shore of Lake Pontchartrain in St. Tammany Parish, Louisiana, United States. The population was 28,781 at the 2020 census, making it the sixteenth-most populous city in Louisiana. It is part of the New Orleans−Metairie−Kenner metropolitan statistical area.

Bayou St. John (French: Bayou Saint-Jean) is a bayou within the city of New Orleans, Louisiana.

The Bayou as a natural feature drained the swampy land of a good portion of what was to become New Orleans, into Lake Pontchartrain. In its natural state, it extended much farther than today; 18th- and early 19th-century maps show it had tributaries or branches (at least seasonally) reaching into what are now the Broadmoor neighborhood, the New Orleans Central Business District just back from St. Charles Avenue above Lee Circle, the Carrollton neighborhood, the Treme neighborhood, and a branch connecting to Bayou Gentilly.

Mandeville is a city in St. Tammany Parish, Louisiana, United States. As of the 2020 United States census, its population was 13,192. Mandeville is located on the north shore of Lake Pontchartrain, south of Interstate 12. It is located directly across the lake from the city of New Orleans and its southshore suburbs. Mandeville is part of the New Orleans-Metairie metropolitan statistical area.

U.S. Highway 51 (US 51) is a part of the United States Numbered Highway System that spans 1,277 miles (2,055 km) from LaPlace, Louisiana to a point north of Hurley, Wisconsin. Within the state of Louisiana, the highway travels 69.12 miles (111.24 km) from the national southern terminus at US 61 in LaPlace to the Mississippi state line north of Kentwood.

After heading north through LaPlace to a junction with Interstate 10 (I-10) west of New Orleans, the highway joins I-55 on a 22-mile-long (35 km) twin-span viaduct across the Manchac Swamp. The bridge, which passes between Lakes Pontchartrain and Maurepas, is the second-longest bridge over water in the United States and serves as a vital hurricane evacuation route for the New Orleans metropolitan area.