Originally determined eligible by the Keeper of the National Register in the Caltrans 1985 Historic Metal Truss Bridges in California Thematic Resources study; its eligibility was reconfirmed in the 2004 Caltrans Historic Bridge Inventory update: Metal Truss Bridges.
The Orestimba Creek Bridge (38C0168) is a steel, rigid-connected, concrete-encased pony truss bridge that was built during a period of experimentation with concrete in bridge design. The bridge, which uses both reinforced concrete and truss technology, is a unique illustration of the innovations of the period. The existing steel truss bridge was encased in concrete in 1918. The encasing was designed by Daniel M. McPhetres, a pioneering engineer in reinforced concrete. The bridge is a one of a kind in California. It was moved from an unknown location in 1918.