US 99 – Piru Gorge : Pyramid Rock and Dam

Virtual Tour of US 99
Piru Gorge

Piru Gorge : Pyramid Rock and Dam

Video on Piru Gorge and Pyramid Lake
by the Historic Highway 99 Association of California

Topographic Map of Pyramid Rock and Vicinity from 1938. Pyramid Rock is in the bottom center of the map.

Pyramid Rock just after construction in 1933. Courtesy – Caltrans

This rock was blasted through in 1931 when US 99 was first constructed through here. Its pyramid-like shape was caused by the blasting for the highway cut. There once were two bridges that went across Piru Creek, one on each side of the cut, but all traces of those bridges are now gone. The southern bridge, visible in the photo above, was constructed from the salvaged remains of the 1916 Castaic Creek bridge (53-0009) . They were removed in 1951 as a part of a cost-saving move. During construction, traffic was either detoured via State 138 and US 6 or held until the roadway was cleared. Piru Creek was rerouted through Pyramid Cut therefore eliminating the need for the widening of two bridges.

1930’s postcard view looking north from Pyramid Cut. The bridge in the foreground was eliminated in 1951. The site is now underneath Pyramid Dam.

Photo of the Pyramid Cut and channel change taken in 1967. Photo Courtesy – Gordon Glattenberg

Blasting at Pyramid Rock in 1951 during widening and channel realignment. Courtesy – Caltrans

Directly behind the rock is Pyramid Dam. Pyramid Dam was completed in 1970 and is a part of the California State Water Project. The dam and reservoir are named after Pyramid Cut/Rock, paying a small homage to the roadway the dam and reservoir submerged under water. I-5 bypassed this segment of US 99 in 1968 due to the construction of this dam. From 1968 to mid-1969, US 99 was still passable from Violin Summit to Smokey Bear Road. About four bridges used to exist in the area of the reservoir.