The city of San Francisco destroyed four large city cemeteries between 1910 to 1947, over 100,000 graves. About 50,000 remains were moved outside the city with their headstones most were not given that option because the families had to pay for that (if they were notified). Those that were not paid for were moved to massed graves. Many were simply paved over. Tons of headstones, tombs, and vaults were ground up and used as building material for street gutters and harbor sea walls. You can still find parts of these by the inscriptions of names and dates in the rubble and gutter stones through out the city. I know this because my relatives remains are now lost for ever.