This sounds like a fun hike/expedition. Maybe I’ll go check it out the next time I’m in Los Angeles.
Information from hikespeak.com:
“Next to Will Rogers State Historic Park there is a shady canyon with a shady past. The ruins of Murphy Ranch, a compound built by Nazi sympathizers in the 1930s have been left behind to decay in Rustic Canyon. For adventuresome hikers, there is a trail entering Rustic Canyon from the east side of Will Rogers SHP. Beyond the end of the trail, there is a long unmaintained path up an overgrown canyon to the ruins. Murphy Ranch can be visited as a 4-mile out and back hike with 200 feet of elevation gain, or as a 5-mile loop with 850 feet of elevation gain that circles back to Will Rogers State Historic Park on the Backbone Trail. An alternate route, and the easiest way to the ruins, is to hike to Murphy Ranch from Sullivan Ridge Fire Road on the east side of Rustic Canyon.”
More information on Rustic Canyon’s Murphy Ranch by Atlas Obscura.