General Law city
Incorporated: May 18, 1989
City Hall: 21825E Copley Dr, Diamond Bar, California 91765
Population (2020 Census): 55,072 (Also see latest State Population Estimates and Earlier decennial Census Counts).
Population Under Age 18 (2020 Census): 18.4%
Population Density (2020 Census): 3,703.6 persons per square mile
Housing Units: 18,819
Persons Per Housing Unit: 2.9
Land Area: 14.87 square miles (38.51 square kilometers)
Water Area: 0.01 square miles (0.01 square kilometers)
Total Area: 14.88 square miles (38.54 square kilometers)
Geographic Coordinates (Latitude/Longitude): 34.001573 -117.817601
Named for the branding iron symbol (a diamond over a bar) of rancher Fredrick Lewis.
City in red below. Click on map for more detailed color map of county.