Sugarloaf Ridge State Park, State park in Mayacamas Mountains, Northern California.

Sugarloaf Ridge State Park spans the Mayacamas Mountains on the Sonoma–Napa county line, with two peaks: a southern one at 1,939 feet and a northern one at 2,265 feet. Its 25 miles of trails climb through oak, madrone and Douglas fir, and Sonoma Creek drops 25 feet over boulders in a seasonal waterfall. Bald Mountain, at 2,729 feet, is the highest point.

The area became a state park in 1964, protecting the region's natural landscape for public use. After closure, community efforts helped restore and reopen the park for visitors.

The Onasáti (Wappo) settled along Sonoma Creek about 1,500 years ago, relying on acorns and berries and known for farming and basketry. A Spanish attempt to take the area in 1823 failed. Cholera later reduced their numbers, and the U.S. government relocated them to reservations.

Trails run from under a mile to 8.8 miles, with elevation gains up to 2,500 feet, so pick a route that matches your fitness. The 25-foot Sonoma Creek Falls is seasonal and best seen in the rainy winter months. Poison oak and stinging nettles grow along Sonoma Creek; stay on trail. Summer highs reach the 90s and lows the 40s, and about 40 inches of rain falls mostly from November to April.

An astronomical observatory within the park allows visitors to observe stars and planets through telescopes under clear night skies. This facility attracts people interested in exploring the cosmos from a location far from city lights.