Location is Bakersfield and the bridge is the Beale Ave. overpass (compare with photo on bottom of p. 78 of Dill's "Southern Pacific's San Joaquin Valley Line." Even the diesel exhaust smudge on the overpass matches).

If the year 1966 is correct, then the photo shows Orange Empire Trolley Museum's Mountain Observation car 599 on the back of the San Joaquin Daylight, No. 51, about to be taken off by a yard switcher so that it can be placed on No. 52 later in the day for the return to Los Angeles. Orange Empire operated excursions using their open-air observation car on the San Joaquin Daylight on both April 2 and April 3 that year, so the photo could have been taken on either day.