This great ridge line trail links the BLM Mule Ridge Trails to the BLM Swazey Recreation Area.
Best done as a clockwise loop starting from Oak Knoll TH then up Salt Creek Loop trail, and back to Oak Knoll on the Mule Ridge Trail (~16 miles). Alternatively, climbing Mule Ridge Trail to the Mule Mountain Loop trail and back to Oak Knoll TH is fun.
More information from the BLM:
The Mule Ridge Trail System consists of about 19 miles of trail connecting Mule Town Road, Placer Street, Whiskeytown National Recreation Area and the Swasey Recreation Area. This trail system crosses a variety of terrain and passes through several mixed vegetation types, with several changes in aspect and elevation along the way. A portion of the trail system follows the historic Princess Mining Ditch and winds through areas rich in mining history from the early days of California gold mining. Primary access to the trail system is from two trailheads off of Muletown Road. Use caution and drive slowly along Muletown Road as it is narrow and curvy. Horse trailers are not recommended beyond the Oak Knoll Trailhead because of this. Please stay on designated trails and do not create shortcuts.
Additional information can be found here