women's competitive teams formed by Chicago Cubs owner Philip K. Wrigley in 1943 when manpower shortages of World War II threatened to stop play and close down major league parks; debuted with 4 teams, ended with 10; skillful athletes often coached by former major-leaguers; players required to attend classes on grooming and social conduct; originally players pitched underhand, used a larger ball, and had shorter base paths; women's game grew to resemble that of the men's major leagues, with more distance between the bases and overhand pitching using a smaller ball; drew nearly 1 million fans at peak in 1948; more than 500 women participated before the league folded in 1954; in 1988 permanent exhibit of league memorabilia unveiled at Natl. Baseball Hall of Fame in Cooperstown, N.Y.; subject of documentary film and feature film with the same title, ‘A League of Their Own' (feature film 1992).