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The Tacoma Narrows Bridge in Washington state, consisting of two suspension bridges, collapsed in 1940 due to a wind-induced harmonic swing. A new, safer bridge was built in 1950, and a sister bridge was added in 2007 to accommodate increasing traffic flow.
The Tacoma Narrows Bridge consists of two suspension bridges at the narrowest point of Puget Sound in the US state of Washington between the city of Tacoma and the Kitsap Peninsula. The first Tacoma Narrows Bridge, the most referenced bridge in popular culture, opened in the summer of 1940 and collapsed four months later. A newer and much safer bridge was built in 1950 and a sister to this bridge was added in 2007.
Seeing the need for a bridge connecting the Kitsap Peninsula and the city of Tacoma, reducing many hours of travel between the two areas, the Washington state legislature authorized a bridge. When the Tacoma Narrows Bridge opened in July 1940, it was the third longest suspension bridge in the world, over 1 mile (1.6 km) long. On November 11, 1940, the bridge suffered a catastrophic failure and collapsed after a strong wind induced a harmonic swing, literally shaking the bridge and earning it the nickname Galloping Gertie. This failure is still used as an example and a cautionary model for engineering and architecture students. The wreck of the original bridge has become an unintended artificial reef and is protected by US federal law.
After WWII, a new bridge was built, using the lessons learned from the failure of the first bridge. The new bridge, also known as the Tacoma Narrows Bridge, was completed in 1950 and is still in use today, having proven to be much more robustly engineered than the previous failed bridge. This second bridge, when built, was still the third longest suspension bridge in the world.
As the whole region developed and the traffic flow increased year on year, it became apparent in the late 1990s that the single bridge was becoming insufficient for the number of vehicles handled daily. A new bridge, designed as a twin to the 1950 bridge, was approved by Washington state voters in 1998. The second span, located next to the existing bridge, was completed in 2007 and traffic flow was configured so that all westbound traffic would use the 1950 bridge and all eastbound traffic would use the new bridge. Today, this pair of bridges is collectively known as the Tacoma Narrows Bridge.
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