I ran across this image recently, from a private collection of travel snapshots:
http://www.splintercat.org/PortlandHikers/1941HighRockWeb.jpg
Looks to be an early lookout, and not the design shown in more recent photos from the 1960s. But here's a question: was there ever a structure in the saddle, just east of the summit, or was that always just a turnaround? Seems like it must have been graded beyond what a road would require.
Tom