I came across this publication recently and thought it was pretty interesting. Good insight into the policies for constructing and maintaining trails in the '30s.
http://ir.library.oregonstate.edu/jspui/bitstream/1957/11691/1/Forest_Trail_Handbook_1935.pdf
I also found that "Oregon's Hidden Wilderness" is available online. This appears to be the original edition and doesn't have the historical narrative on fire lookouts or the topo map insert that the revised edition has. But the price is right.
http://ir.library.oregonstate.edu/jspui/bitstream/1957/10477/1/hik_gui_ore_hid_wil.pdf