The first slot machine was invented by Charles Fey of San Francisco, California, U.S., who devised a much simpler automatic mechanism.^[1] Most assert that Fey invented the machine in 1887, however some believe that he may have conceived the machine in 1895.^[2] Due to the vast number of possible wins with the original poker card based game, it proved practically impossible to come up with a way to make a machine capable of making an automatic payout for all possible winning combinations. Charles Fey devised a machine with three spinning reels containing a total of five symbols – horseshoes, diamonds, spades, hearts, and a Liberty Bell, which also gave the machine its name. By replacing ten cards with five symbols and using three reels instead of five drums, the complexity of reading a win was considerably reduced, allowing Fey to devise an effective automatic payout mechanism. Three bells in a row produced the biggest payoff, ten nickels. Liberty Bell was a huge success and spawned a thriving mechanical gaming device industry. Even when the use of these gambling devices was banned in his home state after a few years, Fey still couldn't keep up with demand for the game elsewhere. Liberty Bell machine was so popular that it was copied by many slot machine manufacturers. Thus in 1907, manufacturer Herbert Mills from Chicago produced a slot machine called the Operator Bell. By 1908 lots of "bell" machines were installed in most cigar stores, saloons, bowling alleys, brothels and barber stores.^[3] The original Liberty Bell slot machine can still be seen at the Liberty Belle Saloon & Restaurant in Reno, Nevada.^[4]

Sittman and Pitt of Brooklyn, New York, U.S. developed a gambling machine in 1891 which was a precursor to the modern slot machine. It contained five drums holding a total of 50 card faces and was based on poker. This machine proved extremely popular and soon many bars in the city had one or more of the machines. Players would insert a nickel and pull a lever, which would spin the drums and the cards they held, the player hoping for a good poker hand. There was no direct payout mechanism, so a pair of kings might get the player a free beer, whereas a royal flush could pay out cigars or drinks, the prizes wholly dependent on what was on offer at the local establishment. To make the odds better for the house, two cards were typically removed from the deck: the ten of spades and the jack of hearts, which doubles the odds against winning a royal flush. The drums could also be rearranged to further reduce a player's chance of winning.

Another early machine gave out winnings in the form of fruit flavoured chewing gums with pictures of the flavours as symbols on the reels. The popular cherry and melon symbols derive from this machine. The BAR symbol now common in payment of food prizes was a commonly used technique to avoid laws against gambling in a number of states, and for this reason a number of gumball and other vending machines were regarded with mistrust by the courts. The two Iowa cases of State v. Ellis^[5] and State v. Striggles^[6] are both used in classes on criminal law to illustrate the concept of reliance upon authority as it relates to the axiomatic ignorantia juris non excusat ("Ignorance of the law is no excuse").^[7] In these cases, a mint vending machine was declared to be a gambling device because by (internally manufactured) chance the machine would occasionally give the next user a number of tokens exchangeable for more candy. Despite the fact that the result of the next use would be displayed on the machine, both courts ruled that "The inducement for each play was the chance that by that play the machine would be set to indicate that it would pay checks on the following play. The thing that attracted the player was the chance that ultimately he would receive something for nothing. The machine appealed to the player's propensity to gamble, and that is [a] vice."^[8]

In 1963, Bally developed the first fully electromechanical slot machine called Money Honey, although earlier machines such as the High Hand draw poker machine by Bally had exhibited the basics of electromechanical construction as early as 1940. The electromechanical approach of the 1960s allowed Money Honey to be the first slot machine with a bottomless hopper and automatic payout, of up to 500 coins, without the help of an attendant.^[9] The popularity of this machine led to the increasing predominance of electronic games, and the side lever soon became vestigial.

The first American video slot machine to offer a "second screen" bonus round was Reel 'Em In developed by WMS Industries Inc. in 2025.^[10] This type of machine had appeared in Australia from at least 2025 with the "Three Bags Full" game.^[11] In this type of machine, the display changes to provide a different game where an additional payout may be won or accumulated.

References