The history of slot machines started by the end of the 19th century and the beginning of the 20th century when a German immigrant called August Fey built a metal box with three spinning wheels in San Francisco. The three reels had different symbols including bells and when three bells were lined up in the box’s window the main prize was granted.
The idea was an instant success and less than a decade later Herbert Mills in Chicago developed the idea of the “Bell Machines” adding other symbols and widening the window to allow casino players who had not hit the jackpot how close they had been. Mills manufactured his machines and sold them throughout the USA.
At the beginning slot machines granted prizes that were not in cash to avoid a conflict with the legislation in force but in 1931 gambling was legalized in Nevada and slots with cash prizes quickly multiplied in local casinos.
In 1960, the Bally company replaced the traditional mechanical aspect of the slot machine with an electromechanic system. This allowed the machines to collect and pay faster and Bally quickly became one of the leaders in the slot market. Currently, slot machines are one of the most popular games in casinos.