Morro Bay, on California's Central Coast, is famous for the massive rock formation that guards the mouth of its natural harbor. A remnant of an ancient volcanic plug, Morro Rock--in Spanish, el Moro, the sentinel--was spotted by explorer Juan Cabrillo as early as 1542. Once sacred to Native Americans, it is now a sanctuary for peregrine falcons and other birds, near secluded dunes, a 2,300-acre national estuary known as the back bay, and eucalyptus...