Many of the people traveling across one of Lake Washington’s floating bridges likely take the innovative spans for granted, but when the lake’s very first floating bridge opened to traffic on July 2, 1940, it was the culminating moment of a remarkable engineering feat.

According to a Washington Secretary of State blog, the Lacey V. Murrow Bridge was the largest and longest floating bridge ever built at that time, and it was the first to be built with reinforced concrete. (It was also known by many as the first I-90 floating bridge.) When it opened, the bridge represented one of “engineering’s greatest triumphs,” in the same category as Boulder Dam and the Golden Gate Bridge.

Construction began on the Murrow Bridge on Jan. 1, 1939. This photo, from the Washington State Department of Transportation Photograph Collection, was taken on Jan. 29, 1940, nearly 71 years ago to the day.

It was rebuilt after part of the bridge sank on Nov. 25, 1990, with the refurbished bridge opening on Sept. 12, 1993. Construction on a second I-90 floating bridge began in April 1986 and was open to traffic on June 4, 1989. That span is known as the Homer Hadley Bridge.