The Glen Helen Amphitheater is a 65,000-capacity amphitheater located in the hills of Glen Helen Regional Park in San Bernardino, California. It is the largest outdoor music venue in the United States. The orchestra, box, and loge sections seat a combined 10,902 people, and the lawn section seats 54,098. It opened in 1993. It was originally built for the US Festival, and again for US Festival 2 US Festival- Wikipedia and originally held 300,000 people "grass only".