The Alvord Lake Bridge was the first reinforced concrete

Reinforced concrete

Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...

 bridge built in America. It was built in 1889 by Ernest L. Ransome

Ernest L. Ransome

Ernest Leslie Ransome was an English-born engineer, architect, and early innovator in reinforced concrete building techniques. Ransome devised the most sophisticated concrete structures in the United States at the time....

, an innovator in reinforced concrete design, mixing equipment, and construction systems. The bridge was constructed as a single arch 64 feet (19.5 m) wide with a 20 feet (6.1 m) span
.
Ransome is believed to have used his patented cold-twisted square steel bar for reinforcement, placed longitudinally in the arch and curved in the same arc. The face of the bridge was scored and hammered to resemble sandstone, the interior features concrete "stalactites" (some of which have subsequently grown due to redeposition of limestone from the concrete).

E.L. Ransome left San Francisco a few years later, frustrated and bitter at the building community's indifference to concrete construction. Ironically, the city's few reinforced concrete structures, including the Alvord Lake Bridge, survived the 1906 earthquake and fire

1906 San Francisco earthquake

The San Francisco earthquake of 1906 was a major earthquake that struck San Francisco, California, and the coast of Northern California at 5:12 a.m. on Wednesday, April 18, 1906. The most widely accepted estimate for the magnitude of the earthquake is a moment magnitude of 7.9; however, other...

 in remarkable shape, vindicating Ransome's faith in the method.

The Alvord Lake Bridge, which arches over a pedestrian entrance to San Francisco's Golden Gate park

Golden Gate Park

Golden Gate Park, located in San Francisco, California, is a large urban park consisting of of public grounds. Configured as a rectangle, it is similar in shape but 20% larger than Central Park in New York, to which it is often compared. It is over three miles long east to west, and about half a...

, was designated a civil engineering landmark by the American Society of Civil Engineers

American Society of Civil Engineers

The American Society of Civil Engineers is a professional body founded in 1852 to represent members of the civil engineering profession worldwide. It is the oldest national engineering society in the United States. ASCE's vision is to have engineers positioned as global leaders who strive toward...

in the 1970s .