This street was named in 1890 as part of Gilman’s Addition to the City of Seattle, which, as noted in Gilman Avenue W and other articles on streets in that addition, was associated with Daniel Hunt Gilman and the Seattle, Lake Shore and Eastern Railway (SLS&E).
In the below excerpt from Thomas W. Prosch’s A Chronological History of Seattle from 1850 to 1897 (1901), some of Gilman’s fellow investors are listed, including Judge Thomas Burke (Burke Avenue N, Burke–Gilman Trail), James D. Smith (W Commodore Way), and Herman Ossian Armour. (The D is a typo, perhaps because of his brother, Philip Danforth Armour’s, middle initial.) The brothers founded the Chicago meatpacking company Armour and Company in 1867.
In his article “The Orphan Railroad and the Rams Horn Right of Way,” in the April 1923 issue of The Washington Historial Quarterly, C.H. Hanford writes of the SLS&E, “A number of Seattle men… subscribed to the capital of the new company to the extent of their means, and having gained so much, Gilman and Judge Burke were successful in inducing Philip D. Armour of Chicago to advance the money required to start the enterprise.” So it is unclear just which Armour brother the street is named for — perhaps it is named for them both.
W Armour Street starts at 1st Avenue N and goes two blocks west to 1st Avenue W, where it is stopped by Rodgers Park. It makes it two more blocks, from 3rd Avenue W to 5th Avenue W, before again being stopped, this time by Mount Pleasant Cemetery. From there it exists in a number of short segments, including paths and stairs, before being stopped, once again, by the Interbay Golf Center at 15th Avenue W. Once across the railroad tracks in Magnolia, there is a nearly uninterrupted ¾ mile stretch from Thorndyke Avenue W to the West Magnolia Playfield at 32nd Avenue W, and then a few more short segments west of 34th Avenue W, ending for good at 46th Avenue W. (There is a shoreline street end off Perkins Lane W, but it is currently inaccessible.)