Welcome to Trione-Annadel State Park in Santa Rosa, California. It is a vibrant 5,000-acre oasis. This park is nestled at the northern edge of Sonoma Valley. Here, volcanic hills, serene woodlands, and open meadows intersect for a uniquely immersive outdoor experience.
What Makes Trione-Annadel State Park Special
This park boasts a rich ecological and cultural tapestry. Remnants of volcanic basalt quarries and the Native American use of obsidian have shaped its history. Thriving oak woodlands and sparkling springs contribute to its outstanding landscape. It’s one of the best-preserved northern oak woodland ecosystems in the region. It offers seasonal wildflower meadows and volcanic rock outcrops. Creeks swell into waterfalls in winter. A man-made lake is alive with bass and bluegill. All seasons bring a new layer of discovery here.
Top Activities and Amenities
State Park, Trails & Loop Network
Covering over 5,000 acres with 40-plus miles of interwoven trails—including an 8.5-mile stretch of the Bay Area Ridge Trail—the park invites hikers, mountain bikers, and equestrians to explore its diverse terrain of grasslands, chaparral, oak forest, and shaded riparian canyons.
Hiking Trails
Notable hikes include the rugged Rough-Go Trail. It features steep switchbacks and rocky outcrops leading to Lake Ilsanjo. The shaded Steve’s “S” Trail crosses obsidian chips. Wide service roads like the Warren Richardson Trail traverse meadows and hillsides.
Mountain Biking & Equestrian Trails
Bicycles and horses are welcome on designated multi-use fire roads and trails—with horse trailer parking, a watering trough, and mounting ramp provided at the Warren Richardson staging area. Riders must stay on named trails and yield appropriately to other users.
Fishing at Lake Ilsanjo
Lake Ilsanjo (26 acres) is stocked with largemouth bass and bluegill. Fishing requires a California license for anglers 16 and older, and visitors must hike in with their gear.
Picnic Areas, Restrooms, Parking & Drinking Water
A visitor center off Channel Drive offers accessible restrooms, potable water, and shaded picnic tables. The main parking lot at the east end of Channel Drive includes parking (day-use vehicle fees apply), accessible features, and drinking water.
Interpretive Exhibits & Wildlife Viewing
Interpretive exhibits at the visitor center convey the park’s geological and cultural legacy. Wildlife enthusiasts may spot deer, squirrels, bobcats, mountain lions, diverse bird species, and even the rare California red-legged frog near Ledson Marsh—one of the park’s seasonal wetland habitats.
Wildflower Viewing
April and May are peak months. During these months, the meadows surrounding both Lake Ilsanjo and Ledson Marsh erupt into colorful wildflower displays. These displays draw photographers and nature lovers.
Camping & Nearby Options
There is no camping or fire facilities within the park itself. Nearby Spring Lake Regional Park and Sugarloaf Ridge State Park offer camping alternatives. They provide full amenities like campsites, showers, and fire rings.
Practical Visitor Tips
- Day-use vehicle fee: typically $7–8; annual state park passes accepted
- Park hours: open daily from sunrise (approx 8 a.m.) until sunset
- No dogs allowed on trails or backcountry—only on paved areas like Channel Drive
- Camping, fires, barbecues, and drones are strictly prohibited
- Bring a valid California fishing license if fishing Lake Ilsanjo
- Stay on designated trails—off-trail travel damages ecosystems
- Bring water, snacks, and layered clothing—summer shade is limited and weather can shift
- Wear approved helmets when biking; yield appropriately to hikers and horses
Local Insight & Seasonal Hidden Gem
For a magical late-spring experience, time your hike to catch the wildflower bloom near Lake Ilsanjo, then stroll over to Ledson Marsh—home to rare red-legged frogs and an array of birdlife. Winter visitors can chase mini waterfalls in Schultz Canyon after rains. Before heading home, drive down to nearby Spring Lake Regional Park’s Environmental Discovery Center to glimpse tide-pool displays, interactive exhibits, and a peaceful lakeside trail—perfect for rounding out your outdoor adventure.
Whether you’re drawn to rugged trails, vibrant blooms, or hidden marsh wildlife, Trione-Annadel State Park delivers a rich tapestry of Sonoma’s natural heritage with every visit.