Back in the 1960's all blackjack games were played with a single deck. Then in 1963 Edward O Thorp released his book Beat the Dealer, which revealed that blackjack was a beatable game for players who learned how to count cards. The book also showed that players using a basic strategy could come close to a break even game.

That book caused the popularity of blackjack to explode as players flocked to the gaming tables trying to beat the game. The casinos countered by adding more decks to make it harder for card counters. Six and eight deck blackjack games are now found in most casinos. Some casinos in Las Vegas and other parts of the country still deal double deck and occasionally single deck games but they are not that common.

Recently some casinos have been bringing back the single deck blackjack games but many of them are changing the rules to give them a bigger house edge. They do this by reducing the payout for a natural blackjack. You need to check the rules before you play a single deck game.