In which year did the original Lake Pontchartrain Causeway open?

The Lake Pontchartrain Causeway, 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 original causeway was a two-lane span, measuring 23.86 miles (38.40 km) in length. It opened in 1956 at a cost of $46 million (equivalent to $390 million in 2023 dollars). This included not just the bridge, but three approach roads on the north end and a long stretch of road on the south end.

The bridges are supported by 9,500 concrete pilings. The two bridges feature a bascule (a moveable bridge with a counterweight that continuously balances a span, or leaf, throughout its upward swing to provide clearance for boat traffic), which spans the navigation channel 8 miles (13 km) south of the north shore.