First automobile drives across Lake Washington Floating Bridge on June 5, 1940.

  • By Greg Lange
  • Posted 1/14/1999
  • Essay 681
See Additional Media

On June 5, 1940, the first automobile crosses the Lake Washington Floating Bridge. The bridge crosses Lake Washington from the Mount Baker neighborhood of Seattle to the north end of Mercer Island and crosses to the east side of Lake Washington south of Bellevue. It carries US 10 (later decommissioned and renamed Interstate 90) across the lake. The bridge is at the time the largest floating structure ever built. In 1967 it will be renamed the Lacey V. Murrow Memorial Bridge.

Designed by the engineer Homer Hadley (1885-1967), the bridge floats on hollow concrete pontoons. This technology was highly innovative at the time.

The bridge, including its approaches, is 3,387 feet long including 25 reinforced-concrete floating pontoons of varying lengths. These are kept in place with 65-ton anchors. During the 18 months it took to construct the bridge, some 3,000 men were continuously employed including 1,200 who worked on site.

Dedication ceremonies were held on July 2, 1940.


Wm. Michael Lawrence, "Lacey V. Murrow Memorial Bridge," (Historic American Engineering Record HAER WA-2), Library of Congress American Memory Website accessed November 1, 2004 (; Judy Gellatly, Mercer Island: The First 100 Years (Mercer Island: Mercer Island Bicentennial Committee, 1977), 91-94; Judy Gellatly, Mercer Island: The First 100 Years (Mercer Island [?]: Mercer Island Bicentennial Committee, 1977), 92-93. Also see:Lucile McDonald, The Lake Washington Story (Seattle: Superior Publishing Company, 1979), 140-141.
Note: This essay was revised on November 1, 2004.

Licensing: This essay is licensed under a Creative Commons license that encourages reproduction with attribution. Credit should be given to both and to the author, and sources must be included with any reproduction. Click the icon for more info. Please note that this Creative Commons license applies to text only, and not to images. For more information regarding individual photos or images, please contact the source noted in the image credit.
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License
Major Support for Provided By: The State of Washington | Patsy Bullitt Collins | Paul G. Allen Family Foundation | Museum Of History & Industry | 4Culture (King County Lodging Tax Revenue) | City of Seattle | City of Bellevue | City of Tacoma | King County | The Peach Foundation | Microsoft Corporation, Other Public and Private Sponsors and Visitors Like You