The Guadalupe River is the southernmost major U.S. river with a Chinook salmon run (see Habitat and Wildlife section below). Much of the river is surrounded by parks. The river's Los Alamitos and Guadalupe Creek tributaries are, in turn, fed by smaller streams flowing from Almaden Quicksilver County Park, home to former mercury mines dating back to when the area was governed by Mexico. The Guadalupe watershed carries precipitation from the slopes of Loma Prieta and Mount Umunhum, the two major peaks of the Sierra Azul, the historical Spanish name ("Blue Mountains") for that half of the Santa Cruz Mountains south of California Highway 17. Two of the Guadalupe River's major tributaries, Los Gatos Creek and Guadalupe Creek have their sources in the Sierra Azul Open Space Preserve on the western and eastern flanks of the Sierra Azul.