Poker is a popular card game with origins that date back centuries. A descendant of the Persian game of As Nas, the earliest known version of poker was played as early as the 16th century in Europe, although it is uncertain where its true birthplace lies. It is widely believed that the game was developed in the United States during the 19th century, with the earliest written reference to the game appearing in Jonathan H. Greenās 1834 book An Exposure of the Arts and Miseries of Gambling. From there, poker spread across the world, becoming one of the most popular gambling games.