The creek drains an area of about 497 square miles (1,290 km2), making it the Santa Clara River's biggest tributary in terms of watershed size.[5][6] Thousands of years ago, Native Americans of the Chumash group lived in the area, but by 500 CE, their former territory along Piru Creek had been occupied by the Tataviam.[9] By the late 19th century, prospectors had discovered traces of calcite on Piru Creek in Lockwood Valley near Frazier Mountain, north of present-day Pyramid Lake.[12] Hiking, camping, off-roading and rock climbing are some of the recreational opportunities in the Los Padres National Forest that surrounds much of the Piru's course.[19] From 0.5 miles (0.80 km) downstream of Pyramid Dam to the Los Angeles-Ventura County line, Piru Creek in various sections is designated a National Wild and Scenic River.In the present day, the uppermost limit of natural fish spawning in the creek is below Pyramid Dam, where a cement culvert adjoining the remains of Highway 99 creates a 15-foot (4.6 m) waterfall.Piru Creek was once a popular spot for both fly fishing and bait-casting anglers as it contained both wild and hatchery-raised rainbow trout, along with largemouth bass.