The history of the San Fernando Valley from its exploration by the 1769 Portola expedition to the annexation of much of it by the City of Los Angeles in 1915 is a story of booms and busts, as cattle ranching, sheep ranching, large-scale wheat farming, and fruit orchards flourished and faded. Throughout its history, settlement in the San Fernando Valley (usually called simply "The Valley") was shaped by availability of reliable water supplies and by proximity to the major transportation routes through the surrounding mountains. Native peoples and the coming of the Spaniards Topography and early settlement Before the flood control measures of the 20th century, the location of human settlements in the San Fernando Valley was constrained by two forces: the necessity of avoiding winter floods and need for year-round water sources to sustain communities through the dry summer and fall months. In winter, torrential downpours over the western-draining watershed of the San Gabriel Mountains entered the northeast Valley through Big Tujunga Canyon, Little Tujunga Canyon, and Pacoima Canyon. These waters spread over the Valley floor in a series of braided washes that was seven miles wide as late as the 1890s, periodically cutting new channels and reusing old ones, before sinking into the gravelly subterranean reservoir below the eastern Valley and continuing their southward journey underground. Only when the waters encountered the rocky roots of the Santa Monica Mountains were they pushed to the surface where they fed a series of tule marshes, sloughs, and the sluggish stream that is now the Los Angeles River. By the time the Spanish conquest of Mexico reached Alta California in 1769, successive groups of indigenous peoples, or Native Americans, had inhabited the area for at least 7,000 years. These peoples tended to settle on well-watered and wooded areas at the Valley's margins. The Tongva, who spoke the Tongva language, a Uto-Aztecan or Shoshonean language, had a series of villages in the southern Valley along or near the river, including Totongna (near modern-day Calabasas), Siutcanga (near Encino; means "place of the oak" in Fernandeño) and Kawengna (which the Spanish would write as Cahuenga; it means "place of the mountain"). In the north-central Valley was an apparently permanent village called Pasakngna (Fernandeño: Paséknga, of unclear etymology), in the lower foothills of the mountains near natural springs and a tule marsh. Other characteristic place-names of Tongva origin in the Valley include Tujunga (Fernandeño: tuxunga,