On May 8, 1973, Carolyn King of Ypsilanti became the first girl to play in the Little League. Little League officials then took away the local charter, and the city of Ypsilanti filed a sex-discrimination suit in response. The U.S. Division of Civil Rights ordered the Little League to drop its boys-only policy. Since 1973, more than 5 million girls have played Little League.
For more information, see Carolyn King wikipedia entry
The Girl in Centerfield available from the MSU Library.