Site information:

Trailhead on Hwy 193/49, just east of Old Foresthill Rd. Bridge spans American River.  The SW end of the bridge is in Placer County, the NE end in El Dorado County.  The plaque is in El Dorado County, so I'm including it there.

38.913408,-121.041017

Plaque information:

State plaque

Plaque text:

Mountain Quarries Railroad Bridge

This bridge, built to carry limestone from nearby quarries to the city of Auburn, was a very early use of reinforced concrete in railroad bridge construction and the largest such railroad bridge in California at the time it was built in 1912. The bridge was designed by John B. Leonard, who became one of California's most renowned pioneers in the design, engineering, and promotion of the use of reinforced concrete.

Registered February 7, 2014

Plaque placed by California State Parks in conjunction with Placer County Historical Foundation.  Dedicated 2014, the 150th anniversary of California State Parks

Registered 2/7/2014