Don't ask why the opening scene of a San Francisco movie was filmed on Bunker Hill in Los Angeles, but it was. The movie opens as Frank Johnson (Ross Elliot) climbs some steep steps while out walking his dog. The location, in fact the whole neighborhood hill, was levelled and carried away in the 1950's, not long after the movie was filmed. The action took place above the Hill Street tunnel at the edge of busy downtown a few blocks from City Hall.
... in the 1930s, this vintage photo shows the Hill Street tunnel, looking north on Hill from 1st, as it still looked when the movie was filmed. The steps climb up on the right side above the tunnel, to the Hill Street block on top where the rest of the opening scene was filmed.