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 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.
The Alameda County Central Railroad Society has maintained a model train exhibit at the fairgrounds since 1959, which has grown to two 15-by-100-foot layouts in O scale and HO scale.Building J, also known as the Amador Pavilion, is a multi-purpose arena and livestock event facility at the fairgrounds. It was briefly home to the Tri-Valley Ranchers of the National Indoor Football League.
Wikipedia https://en.wikipedia.org/wiki/Alameda_County_Fairgrounds
Coordinates 37°39'42.575" N -121°53'19.768" E