Del Mar is a beach city in San Diego County, California, United States, located on the coast of the Pacific Ocean. It was established in 1885 to build a seaside resort. The annual San Diego County Fair has had a permanent home at the Del Mar Fairgrounds since 1936. Horse racing began at the fairgrounds racetrack the following year and is hosted every summer. The city incorporated in 1959 aiming to preserve its small town feel. Its population was 3,954 as of the 2020 census, down from 4,161 at the 2010 census.