The Tacoma Narrows Bridge is one of the most iconic engineering failures of the modern world. Opened on July 1st, 1940, the bridge was the third longest suspension bridge in the world before it collapsed in dramatic fashion just four months later.
Soon after its completion, engineers noticed a disturbing resonance between the structural layout of the bridge and the high winds that whipped through the Tacoma Narrows strait, leading to the bridge's nickname of 'Galloping Gertie.' On November 7th, sustained 40 mph winds caused the bridge to sway violently, trapping one car on its deck and gathering crowds of onlookers before the roadway broke apart and much of the bridge fell into the gorge below.
The driver of the vehicle escaped safely, and no human fatalities occured due to the collapse - though, sadly, a cocker spaniel named Tubby was not as fortunate. The collapse was due to a phenomenon called aeroelastic flutter, in which aerodynamic forces combine with structural modes of vibration to produce rapid periodic motion. A replacement bridge was not built until over a decade later.