John A. Miller was 19 when he started working with LaMarcus Adna Thompson. He soon became Thompson's chief engineer.
Thompson was a Sunday-school teacher from Philadelphia who wanted to provide a wholesome form of entertainment for young people who were frequenting beer gardens for amusement.
Thompson's first "Switchback Railway" was built at Coney Island in 1884. It was a success, and by 1888 Thompson had built about 50 of them in the U.S. and Europe. Thompson's ride was based on a design for an "inclined-plane railway" patented in 1878 by Richard Knudsen of Brooklyn, New York. Knudsen designed a ride consisting of two parallel tracks with gently sloping hills. Cars holding four passengers each traveled down the incline by force of gravity. A lift mechanism raised the cars back up and into place for another trip. Knudsen never transformed his plans into a working ride.