The word slot is an Old French noun, derived from esclot, “to provide with a slot” (also found in Old English). The sense of “to drop a coin into a slot” dates from 1888. By the 1940s, it also acquired the meaning of “taking a position in a slot.” The sense “to fit something into a slot” is from 1966. Today, the word slot is used in a wide range of contexts.
There are no significant restrictions on where you can find slot machines. Nevada allows them in casinos. New Jersey, for example, only allows slot machines in Atlantic City hotels. In Indiana and Louisiana, you can find casino-style gambling only on riverboats, but Mississippi removed that requirement after Hurricane Katrina hit the Gulf Coast. In Delaware, slot machines are legal on three racetracks, but the state lottery commission regulates these facilities. In Wisconsin, you can find slots in bars with as few as five machines.
In modern times, slot machines have become much more sophisticated. Most machines have many pay lines. The original slot machine had five spinning reels, but today there are just three. While the three-reel machine is easier to use, the number of combinations that can be made is limited to 1,000. This limited the ability of manufacturers to offer large jackpots, since the maximum theoretical payout would be 1000 times the amount of money the player bet. In addition, the maximum payout of a slot machine was still very high.