If you search Marin Headlands trail map or Mt. Tam trail maps, you’re likely to find some useful, yet not entirely perfect trail pdfs. My favorite is the Marin Headlands map that is missing distances for half of the trails they have marked. While these are good resources, MapAdventures, a small map shop out of Maine, has really risen to the top in this business.
MapAdventures has produced 3 awesome waterproof trail maps for Northern California including Pt. Reyes, Golden Gate National Recreation Area (Marin Headlands) and Mt. Tam. They are sturdy, but flexible and waterproof, so when you spill Gatorade on them or run in the rain, they will survive!
Each map clearly shows the trails, marks distances between each point, so it’s quite simple to plot a course and calculate the total distance.
These maps are essential for getting lost on the trails, or rather not getting lost. They even tell you which trails you can take your four legged friends on, big bonus!