The longest river in Southern California, the Santa Clarita River also has the distinction of being the last one that has been mostly untouched by the rapid urban sprawl that has effected rivers like the Los Angeles River, however many developers wish to change that and it has been its future has been in controversy for many years, although it appears that developers have little hope of winning due to the its habitat.

Rising from underwater sources in Aliso Canyon near the unincorporated town of Acton it meanders through the Santa Clarita Valley, past Valencia into Ventura County down the Ojai Valley before merging with the Pacific Ocean approximately 100 miles away. It supports a wide variety of vegetation and wildlife including roses, cottonwoods, willows, oaks and grape vines. Another possible reason that has stopped the bulldozers is that it harbors several endangered species of birds including California least tern, and the Brown pelican.

Named by Friar Juan Crespi in the 1769 Portola expedition, it honors St. Clare of Assisi, a founder of the Franciscan order.