Originally determined eligible by the Keeper of the National Register in the Caltrans 1985 Historic Metal Truss Bridges in California Thematic Resources study; its continued eligibility was confirmed in the 2004 Caltrans Historic Bridge Inventory update: Metal Truss Bridges.
Old River Bridge (29 0045) is a movable, rigid-connected, steel-truss bridge with three spans totaling a length of 528 feet. The main (central) span is a Howe through truss that is 256 feet in length and swings over a cylinder pier. The secondary spans are 132 feet each and constructed in a Pratt approach through-truss design. The wood-sided bridge operator's control house is suspended above the deck. The bridge is one of the oldest and longest swing bridges in California.