Simon Building, C. 1907
Several layers of paint over the years have made this very hard to read. I finally was able to establish this as "Central Bldg. & Lbr. Co." as the base sign in black block letters on the north side of the building. Another sign in white letters was later painted over the original but I can only make out a couple of letters followed by "Supply Co."
The lettering is faintly duplicated on the west face of the Simon Building, much of which has been recently altered to provide window space.
You'll also notice that trees have grown significantly in the Pearl District in the last 10 years making many of the signs more difficult to find. Adds to the challenge, right? View this from the corner of NW 14th and Hoyt.