Data from SF Assessor Historical Secured Property Tax Rolls
* Pre-1901 data note: 32,609 units are recorded as built before 1901, with 28,860 of those assigned to the year 1900. The 1900 figure likely represents a placeholder year for buildings whose exact construction date is unknown, particularly those destroyed in the 1906 earthquake and fire. Earlier years show more modest figures: 1890 (1,259 units), 1895 (640 units), 1885 (564 units), 1880 (362 units).