In the early 20th century, Harlem was a stronghold of the Sicilian Mafia, other Italian organized crime groups, and later the Italian-American Mafia. As the ethnic composition of the neighborhood changed, black criminals began to organize themselves similarly. However, rather than compete with the established mobs, gangs concentrated on the "policy racket", also called the numbers game, or "bolita" in East Harlem. This was a gambling scheme similar to a lottery that could be played, illegally, from countless locations around Harlem. According to Francis Ianni, "By 1925 there were thirty black policy banks in Harlem, several of them large enough to collect bets in an area of twenty city blocks and across three or four avenues."