The classic example of a casino, and for long the world's best-known one, which was opened in 1861. The casino has long been a major source of income for the principality of Monaco.

The 20th-century casino, which may also be called a gambling, or gaming, house or club, is a place where gamblers can risk their money against a common gambler, called the banker, or the house. Casinos have almost a uniform character throughout the world. In Europe and South America, they are permitted at many or most holiday resorts and not elsewhere.

In the United States, legal casinos were long operated only in Las Vegas and other locations in Nevada, where various forms of commercialized gambling were permitted. The economy of Las Vegas is almost entirely dependent on the large, luxurious casinos that have operated there since the late 1940s. Casino gambling was introduced in Atlantic City, N.J., in 1978, and from the 1980s casinos also began appearing on various American Indian reservations, which are not subject to state antigambling statutes.

Other legal casinos are located on riverboats; in Deadwood, S.D.; and by special license in Puerto Rico. A general expansion of casino gambling was underway in the United States by the last decade of the 20th century. In South America, there are casinos in Argentina, Colombia, and Ecuador. The casino at Havana, Cuba, was closed after the revolution in 1959.