Rick Hamman has posted several photos of the branch online, mostly taken in narrow gauge years (there's also the famous shot the final run out in 1934 here. California Central Coast Rails and Bruce MacGregor's books, as others have mentioned, are the definitive sources on the subject and each have droves of photos taken in the area. Railroads of Los Gatos, while focusing primarily on Los Gatos and the mountains, does cover some history of operations affecting the branch and a biography of SPC/SP engineer and Boulder Creek native Billy Jones. (Arcadia is temporarily sold out, but Amazon still has copies in stock). Museums of Los Gatos was once in possession of several photos showing the McKeen car which held down the Boulder Creek run for a time, though they've since moved on to another collection.

Most of the Boulder Creek grade is long since obliterated, but one can still vaguely follow the old alignment from the junction at "New Felton" (Roaring Camp) to the other side of Mt. Hermon Rd. The grade from Felton Jct. to Old Felton (the SC&F terminus at the base of the flume, about where the New Leaf Market is today), however, is quite well preserved. I've always wanted to try and find the old Daugherty Extension right-of-way north of B.C., but still haven't had the chance to go exploring.