Recreation
Trione-Annadel State Park lies at the northern edge of Sonoma Valley, adjacent to Spring Lake Regional Park in Santa Rosa. Covering more than 5,200 acres, the park offers over 40 miles of trails for hiking, mountain biking, and horseback riding, along with excellent wildlife viewing.
Its interconnected trail system includes an 8.5-mile segment of the Bay Area Ridge Trail. Visitors can explore a mix of singletrack paths and wide service roads that wind through grasslands, forests, and oak woodlands. Wildflowers bloom in spring—especially around Lake Ilsanjo—while winter rains bring seasonal waterfalls and flowing creeks.
California State Parks is developing a Road and Trail Management Plan (RTMP), expected to be finalized in late 2026. The plan aims to improve access, protect natural resources, and incorporate informal trails into the park’s official network, with strong support and input from the community.
History
Trione-Annadel State Park lies along the eastern edge of Santa Rosa in Sonoma County and reflects a rich blend of natural beauty and human history. For thousands of years, the Wappo and Southern Pomo peoples lived in and stewarded this landscape, relying on its oak woodlands, grasslands, and volcanic terrain. Their connection to the land continues today.
Following European arrival, ranching and farming replaced traditional lifeways. By 1837, the area became part of Los Guilicos Rancho, a 19,000-acre Mexican land grant. In the late 1800s and early 1900s, basalt quarrying emerged as a major industry. Volcanic rock was extracted to create cobblestones used throughout the Bay Area, including San Francisco. Remnants of this era—quarry pits and stone walls—remain visible.
In the mid-20th century, owner Joe Coney transformed the land into a hunting and fishing retreat, creating Lake Ilsanjo and stocking it with game fish. As development pressures grew in the 1960s, local residents and conservationists stepped in to protect the area.
Their efforts led to the creation of Annadel State Park in 1971. In 2016, it was renamed to honor the Trione family’s role in preserving open space in Sonoma County.
Learn more at the official CA State Park website.
Photos by Friends of Trione-Annadel, Zach Fabian, and CA State Parks