The Lake Pontchartrain Causeway in Louisiana is the longest bridge not only in the U.S., but also in the world. It is also the longest over-water highway in the world. The causeway, which is 23.83 miles long, consists of two parallel bridges that cross Lake Pontchartrain in southern Louisiana.
Source: http://en.wikipedia.org/wiki/Lake_Pontchartrain_Causeway
