Seattle has an interesting history. There are a few buildings from the turn of the 20th century; they were often hotels converted into apartments and then occasionally turned into co-ops or condos. In the 1920s, there was a building boom and apartment buildings were thrown up filled with studios and 1-bedrooms for the incoming single men who were taking the new office jobs. Then came The Depression, and there wasn't much building until the late '50s.
As far as lofts go, Seattle didn't have much of a warehouse or factory district outside of the current industrial area. The few buildings in Pioneer Square or the International District have been mostly turned into offices, but you might check http://www.samis.com to see if there's something that suits your fancy in Pioneer Square.
My wife, Cynthia, did the "loft thing" in New York in the 1970s, and when we got here in 1985, we were eager to re-create that, and - well, you don't go to Paris for the Big Macs.
Take a look at listing #449202 - probably smaller than you are looking for. Let me know if you want to take a look-see.