They're not road/highway bridges, but many of the shorter bridges on the UP/former SP main line paralleling CA 99 in the San Joaquin & Sacramento valleys are of wood construction (deck on pilings); while likely not the original structures from the 1870's, they have held up quite well considering that line is one of the most heavily trafficked in the western U.S. Some of the longer river bridges (e.g the Kings and San Joaquin river crossings) were until recently composite wood/steel construction; the outer spans were built on wood pilings sunk into the riverbank, while the spans over the river channels themselves were steel girders atop stone bents; over the last 30 years those bridges have been rebuilt as steel and concrete structures.
