 In its 12 years of history the AAGPBL evolved through many stages.These differences varied from the beginning of the league, progressively extending the length of the base paths and pitching distance and decreasing the size of the ball until the final year of play.For the first five years the circuit used a fastpitch underhand motion, shifted to sidearm in 1947, and never really became baseball until overhand pitching began in 1948.