The Arroyo Seco, Spanish for "dry wash," drains the southwestern San Gabriel Mountains and flows through Pasadena to its confluence with the Los Angeles River. The arroyo's banks became a transportation corridor of trails, railroads, and highways and an enclave for industrialists and artists. For more than a century, its very name evoking more than a stream, it has been a Los Angeles County region overlaying municipalities, eras, and cultures. Eight...