Question: In which district of San Francisco is the structure that Walter S. Johnson famously contributed to preserve?
Sentence (from "Walter S. Johnson"): He was one of the founders of the American Forest Products Corporation, a Fortune 500 company in the 1950s and 1960s, and of Friden, Inc., the Friden Calculating Machine Company, which developed and sold electro-mechanical numerators and office equipment, predecessors of today's computerized counterparts.
Relevant evidence: No