The Diablo Regional Trail is a 31-mile route through six East Bay open spaces: Shell Ridge, Diablo Foothills Regional Park, Mount Diablo State Park, Morgan Territory Regional Preserve, Los Vaqueros watershed, and Round Valley Regional Preserve. Running from Walnut Creek to Brentwood, it is a demanding multi-day backpacking route with elevation gain totaling nearly 10,000 feet. The route crosses a patchwork of oak woodland, chaparral-covered ridges, and grassland hills with long views across the San Francisco Bay Area. It is best suited to experienced backpackers comfortable with limited water sources, hot exposed terrain, and a route that passes through multiple land management agencies. Most backpackers complete the trail in 2-3 days.
East Bay Regional Parks Backpack Sites: Reservations required at least 2 business days in advance, phone-only at (888) 327-2757, Mon-Fri 9am-4pm. As of 2025, backpack camping costs $5 per person ages 16+, free for ages 15 and under (changing to $15 per site in 2026). Maximum 2-night stay. Reservations open in two 6-month blocks (Jan-Jun opens in fall, Jul-Dec opens in late April). Sites close seasonally November-March.
Mount Diablo State Park: Family campgrounds (Live Oak, Junction, Juniper) can be booked via ReserveCalifornia up to 6 months in advance, $30/night plus a $7.99 reservation fee. No hiking permits required. Dogs prohibited on all trails and fire roads. No ground fires; BBQ grills and camp stoves only. No firewood collecting. Alcohol consumption prohibited parkwide. Maximum RV length 20 feet due to winding roads; trailers not permitted.
Dogs: Not allowed at Round Valley Regional Preserve due to endangered San Joaquin kit fox habitat. Dogs are prohibited on Mount Diablo trails but permitted in campgrounds on leash.
Optimal: February-May, when wildflowers bloom (poppies, lupines, globe lilies), temperatures stay moderate, and water sources flow reliably. Late winter and spring bring green hillsides and seasonal waterfalls along Donner Creek, best seen the day after a storm.
Summer (June-September): Extremely hot, with temperatures regularly exceeding 90°F and often reaching 100°F+ during heat waves. There is minimal shade along the exposed ridgelines, and most water sources dry up. Only recommended with a very early morning start and a lot of water carrying capacity. The park may close during extreme fire danger, so call ahead May 15-October 1.
Fall (October-November): Moderate temperatures return but water sources remain unreliable. The grasslands turn gold.
Winter (December-March): Backpack camps closed. Cooler temperatures suit day hiking. Occasional snow is possible at higher elevations.
Water is the critical planning factor. Bring minimum 1 quart per 2 hours of hiking.
Water Sources: Limited and seasonal. Morgan Territory and Round Valley backpack sites have non-potable water year-round (must filter, treat, or boil). Mount Diablo summit has potable water. Assume most natural sources dry by June and don't flow reliably again until the winter rains (November-December). Plan to carry all water between camps during summer and fall.
Resupply: No on-trail resupply. Walnut Creek (north terminus) and Brentwood (southeast terminus) have full services including grocery stores. No mail drop options at trailheads. Most backpackers carry all food for the entire 2-3 day trip.
Cache Strategy: Consider staging water caches if hiking during shoulder seasons, particularly for the long exposed sections through Diablo Foothills.
Heat Exposure: The most dangerous hazard. Minimal shade, exposed ridgelines, and summer temperatures over 100°F create serious risk of heat exhaustion and heat stroke. Early starts (before dawn) are mandatory during warm months. Dogs have died of heat exhaustion here in the past, which shows how serious conditions can get.
Rattlesnakes: Northern Pacific rattlesnakes are common April-October in areas like Diablo Foothills, Morgan Territory, and Round Valley, and most active in warmer weather. Stay on trail, watch where you place hands and feet, and avoid tall grass. Do not run if bitten, as this spreads venom faster.
Mountain Lions: Occasionally spotted. Never approach wildlife. Travel in groups when possible.
Poison Oak: Abundant throughout the trail corridor. The three-lobed oily leaves cause a rash on most people. Stay on trail to minimize contact.
Navigation: The trail crosses multiple jurisdictions and sometimes follows sidewalks, dirt roads, and singletrack. Download offline maps. The route passes under I-680 and crosses Stone Valley Road. A GPS device is recommended for the connecting segments between parks.
Fire Risk: Park closures are possible during extreme fire danger, particularly May 15-October 1. Always check current conditions before departure.
Northern Access (Walnut Creek): From I-680, take the Ygnacio Valley Road exit east. After 3 miles, turn right on Walnut Avenue. After 2 miles, turn right on Oak Grove Road, then bear right onto Castle Rock Road to the staging area. Parking at Castle Rock is limited.
Mitchell Canyon Trailhead (Mount Diablo north entrance): From I-680 in Walnut Creek, exit Ygnacio Valley Road. Turn right on Clayton Road, then right on Mitchell Canyon Road to its end. There is a ranger station, a $6 parking fee, and water and toilets.
Morgan Territory Access: From I-580, take Vasco Road north, turn left on Morgan Territory Road, and follow it to the staging area. It is approximately 4.5 miles to the backpack camp.
Round Valley (southeastern terminus): From Highway 4 in Brentwood, take Marsh Creek Road south and follow it to the staging area. The backpack camp is a 3.6-mile hike from Marsh Creek staging.
Nearest Airport: Oakland International (OAK), approximately 40-50 miles. San Francisco International (SFO) is 50-60 miles.
Shuttles: No dedicated trailhead shuttle services operate. Most backpackers arrange a car shuttle between Walnut Creek and Brentwood (approximately 25 miles by road) or hike point-to-point and use rideshare services.
Road Conditions: All trailhead access roads are paved. The Mount Diablo summit road has steep winding sections with blind curves, so drive cautiously.
Camping Strategy: Most backpackers use the 8/14/8 mile split: Night 1 at Morgan Territory backpack camp (8 miles from Round Valley), Night 2 at Mount Diablo Live Oak or Junction campground (14 miles), then finish with 8 miles to the northern terminus. The reverse direction also works. Junction Campground (6 sites, first-come first-served, $30/night) is the most primitive option in Mount Diablo.
Reservation Timing: Backpack sites open in blocks and can fill quickly for spring weekends. Call exactly when reservations open (9am on release date) for the best availability. Mount Diablo car campgrounds book solid on weekends, but weekday availability is often good.
Water Management: Carry the largest water capacity you own: 4-6 liters minimum for exposed sections in warm weather. Filter or treat the water at backpack camps even though it's listed as available, because reliability varies.
Heat Strategy: Summer attempts require alpine starts (3-4am). Hike until 10am, shelter during peak heat (10am-6pm), and resume evening hiking if needed. Bring electrolyte supplements.
Wildlife: Most rattlesnake encounters happen when hikers step over logs or reach into brush. Use trekking poles to probe ahead. Gaiters add protection.
Navigation Tools: Download offline maps from Save Mount Diablo's regional trail map (available through the Avenza Maps app). Trail signage exists but can be inconsistent where the route follows roads and sidewalks through neighborhoods.
Future Expansion: Save Mount Diablo envisions a 60-70 mile Grand Loop Trail connecting back to Black Diamond Mines Regional Preserve, though several private land gaps remain. The current trail may be extended in coming years.
Training Hikes: Consider day-hiking sections before attempting the full backpack. The Las Trampas to Mount Diablo segment (5 miles, significant elevation gain) is good preparation for the exposure and terrain on the full route.
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