Folsom is a city in Sacramento County, California, United States. The population was 80,454 at the 2020 census. The Nisenan tribe of Nati…Folsom is a city in Sacramento County, California, United States. The population was 80,454 at the 2020 census. The Nisenan tribe of Native Americans had long inhabited the area. The Gold Rush of 1849 brought violence, disease and overwhelming loss for the tribes.