Fernbridge, Concrete arch bridge in Humboldt County, US

Fernbridge is a 1,320-foot reinforced concrete arch bridge designed by John B. Leonard that carries California State Route 211 over the Eel River between Loleta and Ferndale. Its roadway rests on seven shallow segmental arches, each spanning 180 feet, supported by piers 4.6 meters thick. The original wooden approach trestles were replaced by concrete ramps in 1920.

Engineer John B. Leonard designed and built this reinforced concrete bridge in 1911 as a lasting crossing over the river. The project was one of the first applications of this modern construction method in the region.

Locals call it the "Queen of Bridges," a name it carried when it opened in 1911. Each August the town marks the anniversary with a run across the span, as on opening day, and a parade of historic vehicles. A plaque on the northwest approach pylon marks its 1976 civil engineering landmark status.

Fernbridge carries two lanes of State Route 211 between Loleta and Ferndale, with U.S. Highway 101 running close by. The U.S. Geological Survey keeps a stream gauge and a live webcam at the bridge for checking river conditions. Caltrans planned seismic gates at both ends that lower when a magnitude 5.6 quake is detected; installation was pushed to summer 2026.

The selection of reinforced concrete for this bridge was informed by lessons from the 1906 San Francisco earthquake. Engineers observed how this material withstood seismic forces and chose it to ensure durability.