Highgrove is a census-designated place and an unincorporated community in Riverside County, California, United States. The population was 3,988 at the 2010 census, up from 3,445 at the 2000 census. The latest 2020 census shows 7,515 total population, an 88.4% increase from last 2010 census, which makes it the fastest-growing location in entire Riverside County. The city of Riverside, California has plans to annex Highgrove in the near future.