The longest bridge in the United States is the Lake Pontchartrain Causeway, and it is built across Lake Pontchartrain in southeastern Louisiana.

Quick Scoop

  • The Lake Pontchartrain Causeway stretches about 24 miles (around 38 kilometers) over Lake Pontchartrain, making it the longest bridge in the U.S. by total length.
  • It connects the areas of Metairie and Mandeville, just north of New Orleans, and is famous for having a long stretch where drivers cannot see land in either direction.

So, to answer the exact question “the longest bridge in the united states is built across what lake?” — it is built across Lake Pontchartrain.

Information gathered from public forums or data available on the internet and portrayed here.