Seattle's 12th Avenue South (Dearborn Street) Bridge is built in 1911.

  • By Priscilla Long
  • Posted 12/23/2007
  • Essay 8437
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In 1911, Seattle's 12th Avenue South or Dearborn Street Bridge is erected. It is one of the first permanent steel bridges build in Seattle. In 1974 it will be renamed the Jose Rizal Bridge (for the Filipino hero). In 2007 it is the state's oldestĀ steel-arch bridge.

The steel-arch bridge carries 12th Avenue S over Dearborn Street to Beacon Hill. It was a project of Seattle City Engineer R. H. Thomson (1856-1949) and was required after the City regraded the hilly area separating downtown Seattle from the residential areas in the Rainier Valley.

It features "a 171-foot, spandrel-braced arch with Pratt-style web trussing, a 94-foot cantilever span at the south end, and a 96-foot cantilever span to the north" (Holstine and Hobbs). The original bridge had timber approaches.

In the spring of 1917, in the midst of regrading Beacon Hill and during heavy rains, a mudslide destroyed the southern timber approach and shifted the bridge about 30 inches north. The City rebuilt the approach and repaired the bridge.

In 1924 the timber approaches were replaced with six concrete bent approach spans. Trolley lines were removed and a 42-foot-wide roadway was put in place. Further changes were made in 1966 and 1967 during construction of the Interstate 5 and Interstate 90 interchange.

Sources: Craig Holstein and Richard Hobbs, Spanning Washington: Historic Highway Bridges of the Evergreen State (Pullman: WSU Press, 2005), 152-153.

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