Poker has a long and indistinct history. Some hold that it originated in Persia as it closely resembles a game called As Nas and may have been brought to the United States via Persian sailors in New Orleans. This game was played with 25 cards with 5 different suits. This game was played similarly to modern Five Card Stud with many of the hand combinations such as three of a kind. It seems likely that the name Poker descended from the French poque, which originally came from the German pochen, to knock.

The game was reportedly played in New Orleans around the late 1820s, with a deck of 20 cards and players betting on the value of their hands. The earliest known form of Poker was played with a 20-card pack (A-K-Q-J-10) evenly dealt amongst four players. There was no draw, and bets are made on a narrow range of combinations: one pair, two pair, triplets, and full - so called because it is the only combination in which all five cards are active - and four of a kind. Unlike classic Poker, in which the top hand (royal flush) can be tied in another suit, the original top hand consisting of four Aces, or four Kings and an Ace, was absolutely unbeatable. The spread of the game after this seems to have been facilitated by the practice of gambling on Mississippi riverboats.

Soon after this the deck was expanded to the present day 52 cards and the flush was introduced. The additional cards were introduced mostly to allow more players. The game was expanded and developed further during the Civil War, with many of the variants of the game being introduced then, including Five Card Stud. Poker was initially played with only one round of betting with all five cards dealt face down and no draw cards, very similar to todays Five Card Stud game.

Professional gamblers later added variations and rule changes in order to increase the profitability of the game. Wild cards and bluffing became common occurrences and the draw was added around 1850, allowing yet another round of betting. Many of the features of modern Poker, such as the draw and some versions of different hands, as well as the straight and the flush originated in the earlier forms of the British game Brag or Bragg. Brags modern form differs greatly from modern day poker, however.