the first jack in the box restaurant was opened at 6270 el cajon boulevard by robert o. peterson in 1951. the site had originally been a drive-in diner called "topsy's", later renamed "oscar's" after peterson's middle name, which was a classic drive-in where food was served by carhops to patrons in the parking lot. jack in the box was the first drive-through, with the innovation of a two-way intercom that allowed one car to place an order while another car was being served. other restaurants had previously offered drive-up window service, but jack in the box was the first major chain to make drive-through windows the focus of its operation.