History of Slots: From Liberty Bell to Modern Video Slots

The 1890s: Poker Machines and the First Precursors

The slot machine did not begin with spinning fruit. In the 1890s a number of patents were taken out on gambling machines that were precursors to the modern slot, most notably an 1893 design by Sittman and Pitt of Brooklyn, New York. That machine contained five drums holding a total of 50 card faces and was based on poker rather than reels.

It proved extremely popular, and soon many bars in the city had one or more of them. Players would insert a nickel and pull a lever, which spun 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, while a royal flush could pay out cigars or drinks. The prizes depended entirely on what the establishment would offer.

To improve the odds for the house, two cards were typically removed from the deck, the ten of spades and the jack of hearts, doubling the odds against winning a royal flush. The drums could also be rearranged to further reduce a player's chance of winning. That early house-edge logic is the direct ancestor of the mathematical models used in modern slots.

Charles Fey and the Liberty Bell

Because of the vast number of possible wins in the original poker-based game, it proved practically impossible to make a machine capable of awarding an automatic payout for all possible winning combinations. At some time between 1887 and 1895, Charles Fey of San Francisco, California, devised a much simpler automatic mechanism with three spinning reels containing a total of five symbols: horseshoes, diamonds, spades, hearts and a Liberty Bell. The bell 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 design an effective automatic payout mechanism. Three bells in a row produced the biggest payoff, ten nickels (50 cents). Liberty Bell was a huge success and spawned a thriving mechanical gaming device industry.

After a few years, the devices were banned in California, but Fey still could not keep up with the demand for them elsewhere. The Liberty Bell machine was so popular that it was copied by many slot machine manufacturers. The first of these, also called the Liberty Bell, was produced by the manufacturer Herbert Mills in 1907. By 1908, bell machines had been installed in cigar stores, brothels and barber shops.

Fruit Symbols, Gum and Legal Workarounds

The first Liberty Bell machines produced by Mills used the same symbols on the reels as did Charles Fey's original. Soon afterward, another version was produced with patriotic symbols, such as flags and wreaths, on the wheels. Later, a similar machine called the Operator's Bell was produced that included the option of adding a gum-vending attachment.

As the gum offered was fruit-flavoured, fruit symbols were placed on the reels: lemons, cherries, oranges and plums. A bell was retained, and a picture of a stick of Bell-Fruit Gum, the origin of the bar symbol, was also present. This set of symbols proved highly popular and was used by other companies that began to make their own slot machines, including Caille, Watling, Jennings and Pace.

A commonly used technique to avoid gambling laws in several states was to award food prizes. For this reason, several gumball and other vending machines were regarded with mistrust by the courts. The two Iowa cases of State v. Ellis and State v. Striggles are both used in criminal law classes to illustrate the concept of reliance upon authority as it relates to the axiomatic ignorantia juris non excusat, or ignorance of the law is no excuse. In these cases, a mint vending machine was declared to be a gambling device because the machine would, by internally manufactured chance, occasionally give the next user several tokens exchangeable for more candy.

From Mechanical Reels to Random Number Generators

For most of the twentieth century, slot machines were mechanical devices. The reels were physical, the payout mechanism was physical, and the odds were set by the physical arrangement of symbols on each reel. That changed with the arrival of electronics and, later, computer chips.

Modern slot machines are powered by random number generators, or RNGs. Unlike early mechanical machines, where outcomes were set by the physical arrangement of symbols on each reel, electronic slots use computer chips to determine results. Each spin is generated independently, so a machine does not become 'due' for a win based on previous results.

The mechanical operations of early machines have been superseded by electronic components and random number generators. Some modern slots still include a lever as a design nod to the original machines, but on these games the lever no longer controls the outcome.

The Main Categories of Slot Machine Today

Slot machines come in many forms, each offering a different blend of gameplay, visual design and winning potential. Understanding the main categories helps make sense of how the history of slots has branched.

Classic Slots

Also known as three-reel slots, classic slots are modelled after the original mechanical slot machines. They feature simple gameplay, usually requiring you to pull a bar to activate the reels. They also have limited paylines, often just one, and traditional symbols like cherries, bars, bells and sevens. These slots appeal to players who enjoy a nostalgic, straightforward experience with fewer distractions.

Video Slots

Video slots often feature multiple paylines and include a variety of bonus features such as free spins, wilds, multipliers and mini-games.

Progressive Slots

Progressive slots offer some of the largest jackpots available in any casino. These machines are linked across a casino floor, multiple properties, or even online, and a small percentage of each wager contributes to a growing jackpot pool. The prize continues to increase until a player hits the winning combination. Progressive jackpots can range from thousands to millions, making them highly attractive for players chasing life-changing payouts. The odds of hitting the top prize are long, and qualifying for the jackpot may require a maximum bet.

Bonus Slots

Bonus slots feature interactive rounds or special features that go beyond standard spins. These bonuses are usually triggered by specific symbol combinations, such as scatters or bonus icons, and may include free spins, pick-and-win games, wheel spins or multipliers. Bonus rounds often add variety and excitement to the gameplay.

Penny Slots

Penny slots are a popular choice for players who want to enjoy extended playtime on a smaller budget. These machines allow players to bet as little as one cent per line, although the total bet often increases when multiple paylines are activated.

3D Slots

3D slots use advanced graphics technology to create a visually immersive gaming experience. These games often feature cinematic intros, animated characters and rich visual effects that make the reels come to life. While 3D slots function like traditional video slots, their standout design elements appeal to players looking for a more interactive and entertaining experience.

Themed and Branded Slots

Themed slots are built around specific motifs, ranging from ancient civilisations and fantasy worlds to holidays, animals and pop culture. Branded slots are themed around popular franchises, celebrities, movies, TV shows or music artists. They are like themed slots, but these types of slot machines are officially licensed and feature recognisable imagery, audio clips and storylines that fans will instantly connect with.

Specialty Slots

Specialty slots break away from traditional slot formats and offer unique gameplay styles. This category includes skill-based slots, where elements of player input affect outcomes, multi-wheel slots, which feature more than one reel set spinning at the same time, and bingo or keno-style machines, blending lottery elements with slot play.

RTP, Volatility and the Modern Player

Before playing any slot machine, it is important to understand two key concepts: return to player, or RTP, and volatility. RTP is expressed as a percentage and indicates the average amount that a game returns to players over time. It is a long-run theoretical figure, not a prediction of what any individual session will pay.

Volatility refers to the risk level of a slot. High volatility slots offer larger but less frequent payouts, while low volatility slots pay out smaller wins more often. While the RTP may keep your overall wins and losses steady, the volatility will help you understand what to expect for short-term play. Choosing the right balance of RTP and volatility depends on your playing style and bankroll.

It is worth being clear about what RTP is not. It is a long-run theoretical average, not a session prediction or a guaranteed payout. A slot with a 96 percent RTP does not pay back 96 percent of your money in any given session, and no strategy can make a slot more likely to win. The history of slots is partly a history of players learning that lesson.

Where Slots Fit in Ireland Today

In Ireland, slot machines appear in a range of settings, from amusement arcades to licensed bookmakers and online casinos. The terminology, characteristics and regulation of slot machines vary by country of manufacture and use, and Ireland is no exception. Players should check the current rules and terms that apply to any game before playing.

For players in Ireland, the practical history lesson is that the machine in front of you, whether a physical cabinet or an online game, is the product of more than a century of design, mathematics and regulation. The symbols may have changed from bells and fruit to dragons and gods, but the underlying logic of a game of chance remains the same.

If you want to explore the modern end of that history, our classic slots guide covers the three-reel tradition, while the video slots guide looks at the five-reel and Megaways formats that dominate today. For a closer look at how randomness works, see our guide to RNG and provably fair slots.