tributary watersheds, in order of their appearance from southeast to northwest (roughly in downstream order) are: Harding Canyon, Williams Canyon, Silverado Canyon, Ladd Canyon (tributary of Silverado Canyon), Baker Canyon, Black Star Canyon, Fremont Canyon, Blind Canyon, and Weir Canyon on the right bank; and Limestone Canyon and Handy Creek on the left bank. Of the right bank tributaries, the Silverado Canyon, Ladd Canyon and Fremont Canyon sub-watersheds each extend a little into Riverside County. The Silverado/Ladd Canyon subwatershed is the largest, and Williams Canyon is the smallest. Tributaries Santiago Creek has 10 major tributaries along its course, most of which come in while the creek flows through Santiago Canyon. Fremont Canyon is the longest, while Silverado Canyon is by area the largest. The largest sub-tributary watershed is Ladd Canyon, a tributary of Silverado Canyon. Many of the upper tributaries are spring-fed and perennial. An uppercase R stands for right bank, and L is for left bank. Geology The dominant geological feature in the Santiago Creek watershed are the Santa Ana Mountains. The northern portion of the mountains, which Santiago Creek drains, is composed of rocks from the pre-Triassic to the Quaternary (251–2.6 MYA). These rocks consist primarily of slate, sandstone, conglomerate, limestone, and other sedimentary rocks. The uplift of the Santa Ana Mountains began approximately 5.5 million years ago along the Elsinore Fault Zone, which extends north from near its namesake Lake Elsinore area. History Pre-19th century Before the latter 19th century, Santiago Creek and its tributaries were free flowing perennial streams spilling out of Santa Ana Mountains canyons onto the broad, alluvial floodplain. The creek wound on the plain for the rest of its course to its confluence with the Santa Ana River. coast live oaks (Quercus agrifolia), California sycamores (Platanus racemosa), white alders (Alnus rhombifolia), native willows (Salix species), and other riparian habitat vegetation lined the route of the creek and its primary tributaries. The creek and adjacent habitats supported a wide variety of birds, amphibians, fish, insects, and mammals. Native Americans Most of the creek originally lay in the territory of the Acjachemen and the Tongva peoples, two large Native American groups of present-day Orange, Los Angeles, and San Diego Counties. The Acjachemen lived to the south, and the Tongva to the north, of the southwest-running Aliso Creek that flows to the Pacific in an area southeast of the Santiago Creek watershed. An Acjachemen-Tongva boundary terminated