Marin County is where mountain biking was invented. The descents that started the sport happened on Mt. Tamalpais in the early 1970s, and the culture radiated outward across the county's fire roads and ridgelines for decades after. What followed is one of the stranger outcomes in outdoor recreation history: the birthplace of mountain biking became one of the harder places in California to find legal singletrack. According to Marin Trail Stewards, bikes currently have access to only 27% of the area's singletrack.
That number is the baseline. It's what makes 2026 meaningful. Three separate changes to trail access are happening at the same time — a new trail that just opened after a decade in permitting limbo, a water district pilot that expanded e-bike access to fire roads last summer, and an active county review that could open Open Space preserves to Class 1 e-bikes for the first time. They are not coordinated efforts, and they do not apply to the same terrain. But together they represent more movement on this issue than Marin has seen in years. Which change matters to you depends entirely on where you actually ride.
The Trail That Took Ten Years and $650,000 to Open
In January 2026, Marin Trail Stewards officially opened Caballo Rojo at Camp Tamarancho, just outside Fairfax. The trail is one mile long, drops roughly 300 vertical feet, and is built for descending only — purpose-built for mountain bikes, no other use permitted. It is the newest addition to the Tamarancho Loop, which links approximately nine miles of intermediate singletrack through the Serpentine, Wagon Wheel, B-17, Broken Dam, and Goldman trails, with just under 400 feet of elevation gain and loss on the more prominent sections.
The practical function of Caballo Rojo is to solve a problem Tamarancho regulars have known for years. The Alchemist Trail has served as both the primary entry and exit point to the loop, which means descending riders and uphill climbers have been sharing the same narrow path — with downhill bikes eventually spilling onto Iron Springs Road to reach the exit. Caballo Rojo pulls descending riders off Alchemist entirely and exits onto Iron Springs at a safer location with less vehicle interaction. For anyone who has ridden the loop on a weekend morning, the change in flow is immediate.
What took ten years isn't the construction. It's California's environmental review process, combined with a private land easement requiring agreement between the Marin Council of the Boy Scouts of America, the Town of Fairfax, Marin County, and private landowners whose property the trail crosses at its lower end. Marin Trail Stewards and the Access4Bikes community spent over $650,000 on permitting, environmental surveys, engineered drainage, structural elements, and construction. The organization has described it as likely the most expensive project in its history — a significant statement for what is, by trail standards, a one-mile descent.
The broader context is that Marin Trail Stewards pushed through roughly five miles of new trails in 2025, of which Caballo Rojo is the largest single piece. The organization continues to pursue additional projects on private land, where the environmental hurdles are lower, while also advocating for use-change on existing public trails that are already built but closed to bikes. Both strategies are slow. Both are producing results at a pace that, in Marin, counts as meaningful progress.
For current trail status before heading out, tamarancho.report updates conditions in real time, managed by Marin Trail Stewards.
E-Bikes: Three Different Answers Depending on Where You Ride
The e-bike question in Marin is not a single policy. It is a patchwork of rules managed by different agencies, at different stages of review. The answer to "can I ride my e-bike here" depends entirely on which land you are standing on.
Marin Water District Land
Starting July 1, 2025, the Marin Municipal Water District launched a two-year pilot allowing Class 1 e-bikes wherever conventional bikes are permitted — including public roads, parking lots, and unpaved fire roads not signed against such use. This is the most significant expansion of e-bike access on Marin's backcountry terrain to date. Water District land covers a large portion of the Mt. Tam watershed, where many local riders do the bulk of their fire road climbing. Specific roads may carry posted restrictions, so check current signage at the trailhead before riding.
California State Parks
Three state parks in Marin now have Superintendent's Orders allowing Class 1 e-bikes on trails and fire roads as evaluation pilots: China Camp State Park, Angel Island State Park, and Mt. Tamalpais State Parks. Class 1 means pedal-assist up to 20 mph with no throttle. Samuel P. Taylor State Park does not have this order and e-bikes remain prohibited there. The pilots are ongoing evaluations, not permanent policy changes, so status is worth confirming before a planned ride.
Marin County Open Space Preserves
This is the one still in process. Class 1 and Class 2 e-bikes are currently allowed on paved multi-use pathways maintained by the county — including the Mill Valley-Sausalito Path and the Corte Madera Creek Path — but prohibited on all unpaved fire roads and trails within the county's 34 open space preserves. Marin County Parks is actively seeking community feedback on a proposal to allow Class 1 e-bikes on unpaved terrain within those preserves. If the proposal advances, it would open a substantial swath of backcountry to pedal-assist riding for the first time.
One rule applies countywide regardless of land management agency: Class 2 throttle e-bikes require riders to be 16 or older, and helmets are required for all riders of all ages. The county-wide speed limit on paved multi-use pathways is 15 mph, with a 10 mph limit on the Mill Valley-Sausalito section.
The practical summary: on Water District fire roads and inside China Camp, you can ride a Class 1 e-bike legally today. On a county Open Space preserve fire road, you cannot — yet. The gap between those two answers is what the current feedback process is designed to close.
Why These Changes Are Arriving Together
The three shifts above did not result from a single policy decision or coordinated effort. They reflect different organizations, responding to different pressures, on different timelines. What they share is a broader shift in how regulators at every level are treating e-bikes and trail access — no longer a niche question, but a mainstream one.
At the federal level, Rep. Jared Huffman of San Rafael introduced the Safe Standards for Personal E-Bike and E-Moto Specifications Act in March 2026, aimed at creating consistent national classification and labeling standards through the U.S. Consumer Product Safety Commission, alongside age restriction guidance for off-road electric products. The bill's immediate focus is product safety and crash reduction. Its signal to local agencies is that the federal government now views e-bikes as a regulated transportation category requiring coherent rules — which tends to accelerate local policy review.
At the local level, the Caballo Rojo opening demonstrates something that has practical implications beyond one trail: community-funded, professionally permitted trail-building is achievable in Marin even given the regulatory environment. It takes a decade and costs far more than it should. But Marin Trail Stewards' success creates a documented path that other projects can follow and that future advocacy can cite.
For residents who spend time on these trails, the map of what is legal to ride is larger in 2026 than it was in 2024, and it may expand further before year's end depending on the Open Space preserve feedback outcome. One current closure to note: Sorich Park Trail in Terra Linda is closed Monday through Friday from 8 a.m. to 4 p.m. for ongoing trail work, remaining open on weekends and outside those hours.
Separately, Marin County Parks recently completed a 110-acre expansion of St. Hilary's Preserve in Tiburon, adding to the county's open space holdings even as the access and use debates continue on existing land.
The irony that launched this whole conversation — the birthplace of mountain biking having some of the most restrictive trail access in the state — has not been resolved in 2026. But the number of places it no longer applies is growing.
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