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.
Isleton Bridge (24 0051) is a double-leaf Strauss Heel Trunnion Bascule Bridge, with two reinforced-concrete tied-arch through truss spans, rigid-connected Bascule through truss, two concrete girder spans, and a cantilevered operator's control house. In 1953, the original wood deck was replaced by a concrete and steel grid deck. In 2004, the cantilevered operator's control house was replaced with a new compatible cantilevered control house. Important features include open-spandrel balustrade approach with concrete recessed-panel end posts and the same balustrade railing on the concrete arch spans, a cantilevered control house, and reinforced-concrete counterweights, lattice-work metal railings on the steel through truss spans, and wood wheel blocks.