The Lucia Mar Unified School District (LMUSD) is the largest school district in San Luis Obispo County, with about 10,700 students. It covers 550 square miles (1,400 km2) at the southern end of the county, from Shell Beach (at the north end of Pismo Beach) to the county line at the Santa Maria River. This territory encompasses the communities of Shell Beach, Pismo Beach, Grover Beach, Arroyo Grande, Oceano, Halcyon, and Nipomo.