This branch extended north from Santa Monica, along the shore of Santa Monica Bay, to a long wharf constructed in 1893. This wharf, west of Los Angeles, was quickly eclipsed by San Pedro to the south (which had a superior harbor).
According to a historic exhibit on Santa Monica Pier, the wharf and rail line were dismantled by 1911.
Other than this monument and old maps, no trace of the line remains. The rail line was standard gauge, but the segment at the historic marker was built at 5' gauge! Thanks to the Electric Railway Historical Association for identifying this marker.