Just released for public viewing by the San Francisco Assessor-Recorder Carmen Chu: 94,000 photos of houses, shops, and other structures in San Francisco, dating from the 1940s to the 2000s. Visit this webpage for a map showing properties with available photographs, including instructions on requesting an image to view.
Not every house in the city is included, but many are. On the map, once you have located your property lot, mouse over, and a pop-up text block will give the needed information to access the image — the block and lot number, the box number, and the bundle number. Alternately, enter your address on this page.
Once you have those numbers (block/lot, box and bundle), visit this page to fill out a request to have the image pulled.
The new policy from SF History Center: You must visit the SFHC during photo-viewing hours, when they will pull the photo you need at that time. (no order-ahead form anymore [11 May 2019].)
Plan a visit to the SF History Center, on the top floor of the Main Library, Grove and Larkin. Hours for the photo desk at Tuesday and Thursdays 1 to 5pm, and Saturday 10am-12pm and 1-5pm.
You can also order a scan for $20.