The database says that this bridge was built in 1951 but the details on the abutments scream "Art Deco". Further the ATSF Railroad was built in the late 1880s and Colorado Blvd. was laid out that far east at least in the 1920's so I am guessing that this was actually built in 1931.
The right of way, including this and other bridges, was purchased by the Metropolitan Transit District for conversion to public transportation in the form of light rail. The section east of Pasadena, including this bridge, is scheduled for the third extension (the Foothill Extension), tentatively planned after 2011.