The Alameda County Fairgrounds is a 270-acre facility located in Pleasanton, California. It is home to the annual Alameda County Fair, held since 1912, as well as numerous trade shows and community events. Located on its grounds, the Pleasanton Fairgrounds Racetrack was built in 1858, making it the oldest one-mile (1.6 km) horse racing track in the United States. There is a 3,000 seat amphitheater, as well as a 9-hole golf course located within the track's infield.