Sleeper Service Bus - Santa Fe Trail System Night Coach. The California Pacific International Exposition was held in May - November 1935 and February - September 1936. It was held in Balboa Park, San Diego's large central urban park, which had also been the site of the earlier Panama-California Exposition in 1915. The Exposition was held to promote San Diego and support its economy and had hundreds of exhibits on history, the arts, horticulture, ethnic cultures, science, and industry.