Trione-Annadel State Park is a state park of California in the United States. It is situated at the northern edge of Sonoma Valley and is adjacent to Spring Lake Regional Park in Santa Rosa. It offers many recreational activities within its 5,092-acre (2,061 ha) property. The rock formations of Trione-Annadel have played a central role in its history: its volcanic origins, the Native American use of obsidian, the early 1900s mining of cobblestones, and modern hikers' appreciation of its volcanic rock outcrops.