Oceanside is a coastal city located on California's South Coast. It is the third-largest city in San Diego County, California.
The city had a population of 167,086 at the 2010 census. Together with Carlsbad and Vista, it forms a tri-city area. Oceanside is located just south of Marine Corps Base Camp Pendleton. Originally inhabited by Native Americans, the first European explorers arrived in 1769. Spanish missionaries under Father Junipero Serra founded Mission San Luis Rey de Francia on a former site of a Luiseño Indian village on the banks of the San Luis Rey River. In the early 19th century, the introduction of farming and grazing changed the landscape of what would become Oceanside. The area—like all of California—was under Spanish rule, then in 1821 under Mexican rule, and then the U. S. in 1848. In the late 1850s, Andrew Jackson Myers lived in San Joaquin County. A native of LaSalle County, Illinois, he returned in the late 1880s and lived in San Luis Rey. In 1882 Myers moved on the land that was the original town site for Oceanside.