Unfortunately, that 1950's one is likely under copyright (maybe that's why there isn't one at the David Rumsey site).  A big public library like Cleveland might have walk-in access to the national Proquest version of the black and white maps.

CSU-Northridge has an excellent collection of Sanborns and I'm almost positve that they have a mechanism to field remote requests:
   https://maplibrary.csun.edu/ML/sanborn-maps.htm

On Fri, Oct 16, 2015 at 11:23 AM, Ken Grabach <[log in to unmask]> wrote:
Hello, colleagues.
A researcher here at Miami University (Ohio) is looking for access, especially digital access, to Sanborn maps showing the downtown area of San Francisco in the 1950s.  He provided an image of the specific area of interest, which I have attached as a PDF image with this message.

Anyone who is able to provide any assistance with this, please feel free to contact me directly via email.

I may be slow to reply in the next few days, and I have notified the researcher of this.  I will be attending the Depository Library Council meeting and conference next week.  That said, any assistance with access to mapping of this type for the area portrayed would be greatly appreciated.

Ken

Ken Grabach
Maps Librarian
BEST Library, 219D
Miami University Libraries
Oxford, OH  45056  USA