Legend has it the sport of softball began as an indoor game in Chicago in 1887. The ball used in that first game wasn't a ball at all -- it was a boxing glove wrapped into a more spherical shape and hit with a broomstick. As the game evolved, rules became formalized and the game moved outside. In addition to the 16-inch softball preferred for Chicago style, 11- and 12-inch-circumference balls are now used in softball.
Fast Pitch and Slow Pitch
Both fast pitch and slow pitch softball use 11- or 12-inch softballs, depending on the size and age of the players. Boys' and girls' teams with players aged 10 and younger usually use the smaller 11-inch ball. Some women's slow pitch leagues also use the 11-inch ball. Men's slow pitch leagues primarily use the 12-inch ball, as do both men and women playing fast pitch.
A version of slow pitch softball unique to Chicago uses a softer 16-inch ball. The large ball doesn't travel as far when hit, which means few home runs. This made the game popular in the city's school parks and small neighborhood ball fields, since it solved the problem of smaller balls frequently flying out into the streets. Unlike other types of softball, fielders don't wear gloves. Many consider 16-inch softball as much a part of the Chicago's history and character as deep-dish pizza, and it has been a lettered sport in the city's public schools since 1999.