Piru Gorge is one of the more scenic sections of old US 99. Most of it is not submerged, though is no longer open to auto traffic. A large channel change was constructed in 1932 to remove the need for two bridges crossing Piru Creek. This later proved to be a detriment as the creek has since eroded almost the entire channel and a large portion of the highway. This segment was completed in 1933 with three lanes and was widened to four lanes in 1951.