where is diamond bar ca
Diamond Bar is a city in eastern Los Angeles County, California, United States. The population was 55,544 at the 2010 census, down from 56,287 at the 2000 census.It is named after the diamond over a bar branding iron registered in 1918 by ranch owner Frederick E. Lewis.n the California State Senate, Diamond Bar is in the 29th Senate District, represented by Republican Bob Huff. In the California State Assembly, it is in the 55th Assembly District, represented by Republican Ling Ling Chang.