The Old Railroad Grade trail is a great hike for you and Fido if you love a bit of colorful history mixed with your nature exploration. Stretching from Mill Valley to the top of Mount Tamalpais, this historic trail was in use from 1896 until 1930, when it was a popular railroad that took curious tourists for excursions along the scenic route.
The trail has an easy incline, but throughout its 6.6 miles, it rises to 1,300 feet of elevation. You don't have to complete the whole loop, though. There are some parts of the trail that are out-and-back. Multiple trails can be entered off of the main loop. One trail takes you to the East Peak Visitor Center, and a smaller loop will lead you to the Fern Creek and other extended trails.
You will likely see lots of other hikers and cyclists, as the historical West Point Inn is a popular hiker and tourist destination. However, dogs are not allowed in the buildings.
The trails lead throughout a scenic route of wild nature, but there are no amenities, so be sure to pack lots of water for you and Fido. If you take the full trail, you will be enchanted by the beautiful wildflowers and scenic mini-waterfalls that you will have to cross. On clear days, the views extend for miles across the valley.
Dogs are allowed off-leash in certain areas, but you must have one on you at all times. Watch for signs because some areas off of the trail require leashes.
Parking for this trail can be tricky, as there are many narrow streets around the area but only a few that offer parking spaces. It is recommended that if you can't find a close spot, you can begin the hike at the Fern Canyon Road entrance off of Summit Avenue.