Rising in Southern California’s Transverse Ranges, the Santa Ana is an ancient river; geologists suspect that the river’s course predates the uplift of the Santa Ana Mountains, which the river cuts straight through at Santa Ana Canyon. Over millions of years, fed by infrequent but reliably intense storms, the river has carried sediment from the mountains and deposited on the shore, slowly forming a coastal plain that today is home to millions of suburbanites.
The Tongva (Gabrielino) people were among the first to live with the river they called Wanaawna, establishing several villages within sight of the willows and sycamores that lined the riverbed. The reliable water source fed the trees that grew nearby and provided shade. Several Tongva villages lined the river in the area of present-day Orange County, including the village of Hotuuknga near Anaheim and across the river from Olive. Downstream was Pasbegna near present-day Santa Ana.
Roughly once a generation, the Tongva witnessed a flood that mingled the waters of the Santa Ana with those of the San Gabriel and Los Angeles rivers and turned the coastal plain into a giant, ephemeral lake. According to an oral tradition circulated by the Luiseño people of southern Orange County, a great flood (described as a rising ocean) once covered the entire countryside, wiping out the villages on the lowlands and sparing only those camped atop the high ground of Red Hill.