It is situated at the northern edge of Sonoma Valley and is adjacent to Spring Lake Regional Park in Santa Rosa.

These lands were occupied by the Wappo and Pomo people in prehistoric times, who would have primarily inhabited the riparian zones and the marsh perimeter.

[1] Visitors can enjoy the park's diverse wildlife and scenery during any time of the year but are perhaps most rewarded from April through June when most wildflowers are in bloom.

In the oak woodlands, the dominant understory plants are native bunchgrasses, toyon, wild blackberry, coyote brush, and western poison-oak.

Common animals in Annadel include black-tailed deer, western gray squirrel, raccoon, skunk, and opossum.

Many of Annadel's streams are dry in the summer, because rainfall is highly seasonal, with most of the approximately 30 inches (76 cm) of annual precipitation occurring between October and April.

The entirety of Annadel was below the ocean floor as recently as twelve million years ago, around which time massive uplift and volcanic action formed the massif which comprises the park of today.

One of the major soil associations within the park is Goulding cobbly clay loam, which contains roughly 25 percent cobblestones with some basaltic exposures, evidence of the volcanic origins of the Sonoma Mountains.

Much of the soil type in the Yulupa Creek riparian zone consists of Laniger loam, with rhyolite outcrops, another relic of the igneous history.

This site was valuable to the Native American tribes as a source of obsidian, which they used to make scrapers, knives, arrowheads, and spearheads.

Cobblestone quarry operations were a major source of revenue to the Wymores and the Hutchinsons who were the principal land owners in this area around the year 1900.

[1] In addition, excellent black bass and bluegill fishing can be found at the park's largest body of water, Lake Ilsanjo.