Try as I may, I haven’t found a good source explaining when or even why Seattle began marking intersections with metal letter street names embedded in concrete sidewalks. It has been suggested that the practice developed before there were street names posted on telephone poles. It has also been suggested that developers who platted our streets were required to insert the names in the sidewalks. 

So much for urban myths! On Queen Anne almost all the platting took place before the advent of concrete sidewalks. Also, the consistent size and font across all of Queen Anne and elsewhere in the city suggests that even after we started having concrete sidewalks, it may not have been the developers who installed the names. My guess is that once the wooden sidewalks began to rot, the city laid up sidewalks and had a store of those matching letters that it used at every intersection.

My guess is practically confirmed by what we know of the history of street paving.

According to A Narrative History of the Engineering Department, the first concrete pavement in Seattle was laid in 1919 (p. 105). The word pavement apparently related to the roadway. The earliest, and truth be told, only reference to concrete sidewalks that I’ve been able to locate in the Seattle Municipal Archives relates to a petition submitted on November 14, 1902 by August C. Anderson protesting a payment of $844.95 that he paid for the construction of a concrete sidewalk on both sides of Eastlake Avenue between Howell Street and Mercer Street, under Ordinance 7928 creating Local Improvement District 578 (SMA 990027 transcript).

UPDATE to all the guessing which it turns out was much closer to the truth than I imagined.  David Williams, the prolific author of articles and books about the geology, geography and history of Seattle including the 2017 Seattle Walks: Discovering History and Nature in the City, knew all along. In a  July 2015 post, David identify City Resolution 387, passed on October 20, 1902 as the reason for the embedded names.  It reads: 

A Resolution declaring that all concrete sidewalks laid in the City of Seattle shall have the names of the streets countersunk in plain letters at the street intersections, and instructing the Board of Public Works to provide for this being done in all contracts and permits for such sidewalks; also directing the Board of Public Works to procure samples of durable and suitable street signs, together with prices, and to transmit them to the City Council with a cost estimate.

Mr. Anderson would be shocked to see what happened to the east side of the street around 1962 when I-5 ploughed through the neighborhood, but his petition gives a vague sense of when the city gave up wooden sidewalks for the more durable concrete ones and when it may have begun insisting on the metal names at intersections.

H. Ambrose Kiehl took this 1895 photo (UW Special Collections) of his family's house on Republican St. when he worked as the Army’s photographer at Fort Lawton and before the family moved up the hill to Fifth W. and W. Galer. Note the wooden sidewalks and unpaved surface of the roadway.

Recently, Julia Herschensohn photographed some of the interesting metal names she’s located on her morning walks around the hill. The misspellings such as Liane St. above make me chortle, so do Julia's shoes.

Here is one set of embedded letters at the intersection of Galer and Second W. that makes it a real stumper.

Adding an H and an I to the beginning of the first word and a D at the end along with a C to make 'place,' transforms this mysterious set of letters into HIGHLAND PLACE. It is a street name that has changed!

The metal street names embedded at all the intersections on the 2018 Mercer Street rebuild show the city and its traffic engineers tipping their hats to a Seattle tradition. It may be that the huge size of these newer street names reflects an aging population, a decline in visual acuity in the general population or the traffic engineers' desire to tease us with a font size that reflects the massiveness of the roadway they’ve built in our 21st century automobile age.

In any case, there is no need to tell you where I took this photograph. 

It would be lovely to learn for sure how, when and why the city started identifying streets in this delightful way.  In the meantime, here are the letters which got me interested in this problem. They are on my street corner and remain my favorites.