San Luis Obispo County is on the Central Coast of California. As of the 2020 census, the population was 282,424. The county seat is San Luis Obispo. The County of San Luis Obispo government was established in 1850 as one of the original 27 counties in California. The region's approximate 3,300 square miles and 100 miles of coastline. San Luis County is the home of Cal Poly SLO.