Robert Louis Stevenson State Park

Mount Saint Helena, much of which lies within this park, is the highest point in the San Francisco Bay Area. On its slopes is a variety of plant communities which well illustrate exposure and altitudinal differences. Among those present are chaparral, a small amount of coastal prairie, foothill woodland, northern oak woodland, mixed evergreen, and a Douglas fir forest. In Rattlesnake Canyon there is a stand of redwoods, Sequoia sempervirens, which are isolated from the nearest populations by some 15 kilometers (9 miles).

Eight species of Arctostaphylos, seven of Ceanothus, and six Quercus are found within the park limits. The California nutmeg, Torreya californica, occurs here in some abundance. Among the pines, which include Pinus attenuata, Pinus ponderosa, Pinus sabiniana and Pinus lambertiana, the latter is near its southern distributional limit in the Northern Coast Range. The nearest population to the south is a disjunct in the Santa Lucias in Monterey County, some 280 kilometers (175 miles) distant. The incense cedar, Calocedrus decurrens, which occurs here, exhibits a similar distributional gap.

Four species of rare plants occur within the park: Eriogonum luteolum var. caninum, Erythronium helenae, Fritillaria purdyi and Lupinus sericatus.

Geologically, Mount Saint Helena is composed primarily of Sonoma volcanics, which date to the Pliocene, with some serpentine exposures. The volcanics are predominantly andesitic with some rhyolitic tuffs, tuff-breccia and welded tuffs. The mountain, though composed of volcanics from unknown eruptive sources, is not a volcano.

Integrity: Portions are developed for park facilities and there are various structures on the south peak and elsewhere. Fires have burned extensive sections of the mountain. The Silverado Mine, producer of gold and silver, is located within the park. There are also some inholdings in the park.

Use: Research, educational, observational, present.

March 1977