The Mayacmas Mountains (often called the Mayacamas Mountains) are located in northwestern California in the United States. The mountains, one of the California Coast Ranges, are found south of the Mendocino Range, west of Clear Lake, and east of Ukiah, and extend south into Napa and Sonoma counties. The range stretches for in a northwest-southeasterly direction, and reaches an elevation of above sea level at Cobb Mountain in the southeastern part of the chain. There are several other peaks over 2,500 feet (750 m), including Mount Saint Helena and Hood Mountain. These peaks are sufficiently high to retain some snow cover in winter. Several streams rise in the Mayacmas Mountains including Mark West Creek, Sonoma Creek, Calabazas Creek, Arroyo Seco Creek, Putah Creek, and Santa Rosa Creek. In prehistoric times of about ten million years ago, these mountains are thought to have been densely forested in Mendocino Cypress.