Prior to the 1850s, Nob Hill was called California Hill (after California Street, which climbs its steep eastern face), but was renamed after the Central Pacific Railroad’s Big Four – known as the Nobs – who built their mansions on the hill… The neighborhood was destroyed in the 1906 earthquake and fire, except for the granite walls surrounding the Stanford, Crocker, Huntington and Hopkins mansions. Those walls remain and black scars caused by smoke from the intense fires that burned after the quake can still be seen.
Also gutted by the fires was the newly completed Fairmont Hotel at Mason and California Streets, as well as the James C. Flood Mansion. Both structures had stone exteriors that survived the fires, and both buildings were subsequently cleaned and refurbished. The Fairmont Hotel remains in operation to this day and the Flood Mansion is the headquarters of the exclusive Pacific-Union Club — quoted from Wikipedia