The Lake Pontchartrain Causeway

The Lake Pontchartrain Causeway, connecting Metairie to Mandeville across Lake Pontchartrain north of New Orleans, held the record as the longest bridge over water in the world from its completion in 1956 until 2011. The southbound span stretches 23.83 miles, and at its midpoint the shoreline is no longer visible in any direction. Fog and storms can reduce visibility to nearly zero, and for years drivers could use radio-controlled markers embedded in the road to stay on course when they couldn't see anything else.

Source: Wikipedia