That would have been my assumption — and, if not Seattle, then surely Tacoma? But no — apparently it was Temple Emanu-El in Spokane, built in 1892 at the corner of 3rd and Madison (the land is now a Lexus delership).
Here's Historylink.org's essay on the history of the Spokane Jewish community, and the story from the ADL that called this to my attention. (The historical plaque had been vandalized earlier this year, and was rededicated on June 25.)