Leon Moisseiff was the leading suspension bridge engineer in the United States of America in the 1920s and 1930s. Born in Latvia, he immigrated to the United States with his family at the age of 19 and graduated from Columbia University with a degree in civil engineering in 1895. He began his career in New York, and gained a national reputation for his design for the Manhattan Bridge over the East River. He was also the chief engineer for the Benjamin Franklin Bridge across the Delaware River. He was an early advocate of all-steel bridges, which began to replace concrete and stone structures in the 1920s. He became known for his work on "deflection theory," which held that the longer bridges were the more flexible they could be. He applied this theory to the the famed Golden Gate Bridge, on which he was a consulting engineer. He was also one of the designers of the San Francisco-Oakland Bay Bridge, which opened in 1936. He called the Tacoma Narrows Bridge, of which he was the primary designer, the "most beautiful bridge in the world." However, he lost his good reputation when this narrow span across the Puget Sound in Washington State collapsed in a minor windstorm four months after it opened in 1940. The dramatic film of the bridge's collapse, as a twisting motion added to the stress of longitudinal waves along the span, is still shown to engineering, architecture, and physics students.
Moisseiff died of a heart attack in 1943. Though he had designed many other famous spans, the Narrows collapse overshadowed them all. It became a symbol of failed engineering and the dangers of arrogance in design. For more information about Moiseiff and his career, see Henry Petroski, _Engineers of Dreams: Great Bridge Builders and the Spanning of America_ (New York, 1995).