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Some of the blog posts I’m most proud of here are the ones in my “ultimate guides” series. So far I’ve written ultimate guides to United States lottery games, greyhound racing, and Atlantic City casinos.

Slot machines were invented by Charles Fey in 1895. Fey lived in San Francisco and worked as a mechanic. He created an entirely mechanical, three reel machine that used gears and levers to make it work. Fey named the first slot machine “Liberty Bell” since each of the reels featured an image of the cracked Liberty Bell. Slot machine technicians can learn on the job or through independent study of manuals. However, completing a training program can help technicians keep up-to-date on new machines and become more.

Today, though, I’m writing about something even bigger—the king of casino gambling games.

Today’s post is the ultimate guide to slots and slot machines.

My goal with this post is to share everything you might need to know to play slot machines intelligently in a casino.

Here are the topics covered in this post:

The history of these games
Differences in gameplay from one country to another
How to play slots in Atlantic City, Las Vegas, Reno, or anywhere else
How the payback percentage, probability and odds work
Which different kinds of games are available
The most popular games
How slot machine tournaments work
Which of those games are best for the discerning gambler?
Questions and answers

The History of Slot Machines

If you’ve read anything about antique slot machines or about the invention of these games, you’ve heard of Charles Fey. He was a mechanic living in San Francisco. In 1887, he invented a game with 3 spinning reels. Each of these reels had 5 symbols on them:

Diamonds
Hearts
Horseshoes
Liberty Bell
Spades

The Liberty Bell

You’ll notice a playing card theme here, but you’ll also notice horseshoes—symbols of good luck. And the Liberty Bell is the symbol from which this prototypical slot machine game gets its name. The game originally required an attendant to pay off wins, but he continued working on and improving the machines. Eventually (by 1898), you could play a Liberty Bell slot machine and win a whopping 50 cents from the machine directly.

A Tradition of Outsmarting the Law

The games were quickly made illegal because of their gambling nature. But entrepreneurs are creative, and Fey (and other imitators) got around these restrictions by paying off winnings in candy. This is where we get the ubiquitous fruit and bar symbols seen still on these games today. The fruit symbols used to represent the flavor of the candy won. The bar symbols represented sticks of chewing gum.

In some ways, history keeps repeating itself. I live in Texas, and you’ll find slot machines called “8-liners” throughout the state. I’ve seen them in bars, in gas stations, and in “game rooms”. Since slot machines are (strictly speaking) illegal in Texas, these games don’t pay off in cash.

Instead, you get points which you can use toward prizes. I spent some time in a game room in a small town in Texas where you could literally cash in these points for canned goods like corn. They also had a cheap set of gardening tools available.

I’ve also played 8-liners in bars where if you won you had to visit the owner of the bar on Friday to pick up “an envelope”. This envelope had your cash winnings in it. But God forbid you ask for an envelope if the owner didn’t know who you were.

These are just examples from my personal experience of clever entrepreneurs skirting anti-gambling laws to continue to offer slot machine games to their customers. In that respect, things have changed little since the 1890s.

In fact, these gambling machines changed very little for decades, although they did become fixtures in the casinos. For years, these games were considered a distraction for the wives of the “real” gamblers—the men who were playing blackjack, craps, and poker. They were found in the places in the casino where the management thought they’d be more likely to attract the attention of these women.

Bally Technologies, Money Honey, and New Electro-Mechanical Games

Things started to change in the industry in the 1960s with the introduction of the first electro-mechanical slot machines. Bally Technologies invented a game called Money Honey, which incorporated a combination of electronic components. These gizmos enabled the designers to accept multi-coin bets. These games also ran faster.

Faster games with higher payouts increased the popularity of such machines, but they didn’t take over the casino floors immediately. This has been a gradual process that hasn’t stopped. But the invention of electro-mechanical machines like Money Honey was the first step in that direction.

Video Slots Like Fortune Coin and Megabucks Change Everything

The industry took off with the invention of video slots in 1979. The importance of the developments made in the 1980s can’t be overstated. The first of these was called Fortune Coin, and it was soon acquired by IGT, the largest manufacturer of casino games in the world. Believe it or not, it was initially distrusted by gamblers. They assumed that a game powered by computer animation would inevitably be rigged and impossible to win.

By 1986, these computerized games made it possible to link multiple games to the same ever-increasing jackpot. These games are now called progressive slots, and the first—and still most famous—example of these games is called MegaBucks. The jackpot for this network of games regularly surpasses $10 million.

These larger jackpots became available because of the lack of restrictions on number of symbols on each reel. With a mechanical slot machine, you’re limited to probably 20 symbols per reel max. And since such a game is mechanical, it’s hard to adjust the probability of a symbol coming up. Each stop had an equal chance of happening.

But with a computerized game, you can program one symbol to come up once every 20 spins and another to come up once every 40 spins. The games now use PARs sheets to delineate those probabilities. The designers and the casinos know what the odds are on these games. The public doesn’t have access to this information, though.

Over the last 30-40 years, slot machines have become the most popular game in the casino. Just a decade ago, you’d often see the following factoid on the Internet:

65%-70% of a casino’s revenue comes from the gambling machines.

But that’s changed. I read a book recently which claimed that in most casinos, slots make up 80% or more of that casino’s revenue.

This is a seismic shift in gambling practices in a casino.

The Internet Changes Everything Again

In the 1990s, the Internet became a thing. It didn’t take long for gambling entrepreneurs to realize that you could use similar computer technology to offer the same kinds of games over the Internet. The Web also allowed these operators to offer their games to players in areas where gambling was illegal. (Remember—that’s a tradition in the industry.)

The thinking is that an offshore casino is regulated by the laws where it’s located. If gambling on the Web is legal in Costa Rica, for example, it’s legal for someone in Texas to gamble online there. Their contention is that the wagering is taking place where the server in Costa Rica is.

The federal government in the United States takes a less enlightened stance on this idea. They’ve made it clear that offshore companies offering gambling games to United States players are breaking the law. They’re less close-minded about whether the players are breaking the laws.

The Future

As Criswell points out in the great Ed Wood movie Plan 9 from Outer Space, we’re all interested in the future, because that’s where we’re going to spend the rest of our lives. But who knows what the future holds for slot machine gambling?

It’s clear to me that we’ll continue to see innovations which make these games even more compelling and addictive. The legal climate in the United States seems to be trending toward legalization. Just in my own lifetime, I’ve seen gambling become something that people had to fly to Nevada or to New Jersey to do. Now I can just drive an hour north to the Winstar Casino to spin the reels and try my luck.

Slot machines are going to continue to become more interactive and profitable for the casinos. Eventually, I’m going to predict that they’ll become too interactive and addictive. At that point, the government might start restricting gambling on a legal basis again. The pendulum seems to swing back and forth with such things, at least in the USA.

Most of the research for this section was done using