The Tacoma Narrows Bridge--affectionately known as "Galloping Gertie"--was the third longest suspension bridge in the world. Before it collapsed, that is. On November 7, 1940, the largest structure ever to fall in the water did just that and immortalized Tacoma in high school physics textbooks for years to come.
Why did the Bridge "gallop"?
Wind-induced vibrations running the length of the bridge caused the Bridge surface to undulate like a roller-coaster. The movements were even present during construction. Proper ventilation was designed, but due to budget cuts and politics, the bridge was built without it. When it opened on July 1, 1940, drivers would sometimes see the car in front of them disappear due to the galloping road motion.
Why did it collapse?
Winds between 35 and 46 miles an hour caused the bridge to begin to twist in addition to its usual motion, which quickly prompted officials to close the bridge. After about an hour of twisting, the spans began to fall into the Puget Sound. The bridge had opened only four months before.
Did they replace the Bridge?
Yes, the new Tacoma Narrows Bridge was built in 1950 and is still in use today (by the way, it doesn't gallop). Over a mile long, it connects Tacoma with Gig Harbor and the Key Peninsula. An even newer bridge is under construction next to the Tacoma Narrows Bridge to accommodate the rising number of commuters and visitors who use the bridge. The new bridge will be built on the south side of the current bridge so as not to disturb the ruins of Galloping Gertie, which was declared a National Historic Site in 1992.
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