United States cities with teams from four major league sports

There are 12 United States metropolitan areas that are home to teams that compete in each of the four major professional sports leagues in the United States and Canada: Major League Baseball (MLB), the National Basketball Association (NBA), the National Football League (NFL), and the National Hockey League (NHL). These leagues are sometimes called the "Big Four", in reference to their prominent position in North American sports.

Source: Wikipedia — United States cities with teams from four major league sports (CC BY-SA 4.0)