According to legend, the spitball made its debut on May 29, 1905, introduced by Dodger hurler Elmer Stricklett in a game against the New York Giants. Stricklett managed to defeat the Giants, 4-3.
While it is widely accepted that Stricklett was one of the early pioneers of the spitball, Stricklett himself denied that he actually invented the pitch. Stricklett did, however, claim to be the first pitcher to master the pitch and to feature it as the key pitch in his arsenal.
Elmer Stricklett (Wikipedia)
