Softball, a variant of baseball and a popular participant sport, particularly in the United States. It is generally agreed that softball developed from a game called indoor baseball, first played in Chicago in 1887. It became known in the United States by various names, such as kitten ball, mush ball, diamond ball, indoor–outdoor, and playground ball. There were wide variances in playing rules, size and type of playing equipment, and dimensions of the playing field.
Two women playing softball in 1919. National Photo Company Collection/Library of Congress, Washington, D.C. (reproduction no. LC-DIG-npcc-00406)
The Chicago indoor baseball team, c. 1897. According to baseball historian Paul Dickson, this is believed to be the first photo of a softball, or indoor baseball, team. Library of Congress, Washington, D.C. (reproduction no. LC-DIG-ppmsca-18407)