Sidewalk Prisms
The purple sidewalk prisms in the pavement around Pioneer Square are an opportunity to observe Seattle’s changeable landscape. Much like the seawall, sidewalk prisms are tangible reminders of the ways that the city’s residents have altered the physical environment to suit their needs.
After the Great Fire of 1889, the Seattle City Council seized the opportunity that the wholesale destruction of the business district to raise and widen the streets. Elevating the streets would address Seattle’s desperate sewage problem and widening the roads would alleviate the traffic that had formerly resulted from the “narrowness and crookedness of the streets.” Not everyone, however, supported the plan. Henry Yesler threatened to sue the city when the changes to the streets delayed construction on the Pioneer Building. Despite Yesler’s disapproval, the plan to alter the streets went forward and most of the Pioneer Square streets were raised by an average of five feet per block.[1]
The streets were raised but the sidewalks remained at their pre-fire elevation until the city passed an ordinance requiring permanent sidewalks to be built at the new street level in 1893. Thus the sidewalks were raised and the building façades adjusted as the points of entry jumped to the second floor. It is still possible to identify some of these old sidewalks because they have glass sidewalk prisms, or vault lights, embedded in them. The glass has turned purple over time due to its high manganese content, but the purpose of the prisms is to let light into the subterranean canyons below the modern sidewalks, which have historically been used for storage. According to one history of Seattle, there are approximately 19,000 sidewalk prisms “dotting the sidewalks of Pioneer Square.”[2]
[1] David Williams, Too High and Too Steep: Reshaping Seattle’s Topography (Seattle: University of Washington Press, 2015), 55-56; “Two Duties,” Seattle Post-Intelligencer, June 12, 1889.
[2] Williams, Too High and Too Steep, 55-56.
Credits and Sources:
Description by Madison Heslop on behalf of the American Society for Environmental History.
“Two Duties.” Seattle Post-Intelligencer. June 12, 1889.
Williams, David B. Too High and Too Steep: Reshaping Seattle’s Topography. Seattle: University of Washington Press, 2015.
