Campo is an unincorporated community in the Mountain Empire area of southeastern San Diego County, California, United States. The population was 2,955 at the 2020 United States census, up from 2,684 at the 2010 census. For statistical purposes, the United States Census Bureau has defined Campo as a census-designated place. The census definition …Campo is an unincorporated community in the Mountain Empire area of southeastern San Diego County, California, United States. The population was 2,955 at the 2020 United States census, up from 2,684 at the 2010 census. For statistical purposes, the United States Census Bureau has defined Campo as a census-designated place. The census definition of the area may not precisely correspond to local understanding of the area with the same name.