Trivia Tuesday, September 30

Test your roads and bridges industry knowledge in our new weekly series!

Sept. 30, 2025

2 min read

Last week’s answer

Question: What is the longest bridge on a U.S. interstate highway?

Answer: The Manchac Swamp Bridge in Louisiana

The Manchac Swamp Bridge carries Interstate 55 and U.S. Route 51 over the Manchac Swamp in eastern Louisiana. It connects St. John the Baptist Parish and Tangipahoa Parish.

Opened in 1979, the structure spans 22.8 miles. On top of being the longest bridge on the U.S. Interstate Highway System, it is one of the longest bridges in the world over water and one of the longest toll-free bridges.

The original Manchac Swamp Bridge collapsed in 1976 after a towboat collided with it. Repairs totaled $600,000.

Sources: WorldAtlas, Louisiana History Minute