Is Old Man Rock still there?
According to the
Stone Faces Gazetteer, the exact location is unknown. But I'm happy to report that I found a version of the Mount Wilson Hotel brochure which gives its location as, "One-half mile down Toll Road and an eighth of a mile down trail." This places it somewhere in the vicinity of Martin's Camp, AKA the saddle between Mt. Wilson and Mt. Harvard.
The Mount Wilson Hotel revised this brochure over the years, and I really can't say when this one was published (The eBay seller says ca1930s, but who knows? The pictured hotel is the second one, replacing the original which burned down in 1913). I will cross-post this to a facebook group for Mount Wilson, and maybe somebody will stroll down from the observatory and send us a nice photo. And the Stone Faces Gazetteer will be certainly be over the moon.
eBay
eBay
This article includes a wider photo and a bit of information. (Not working at this moment.)
Here's the article from another source:
Notes on a visit to Mount Wilson, Leo Holcomb, Page 471, Popular Astronomy, October 1914
Update: the brochure is from 1936 or earlier, because that is when the Pasadena and Mount Wilson Toll Road Company was renamed the Mount Wilson Hotel Company.