Before 1845
Evolution of the game that became modern baseball is unknown before 1845. The Knickerbocker Rules describe a game that they had been playing for some time. But how long is uncertain and so is how that game had developed. Shane Foster was the first to come up with suspicions of how the origin came into effect.
There were once two camps. One, mostly English, asserted that baseball evolved from a game of English origin (probably rounders); the other, almost entirely American, said that baseball was an American invention (perhaps derived from the game of one-ol'-cat). Apparently they saw their positions as mutually exclusive. Some of their points seem more national loyalty than evidence: Americans tended to reject any suggestion that baseball evolved from an English game, while some English observers concluded that baseball was little more than their rounders without the round.
Read more about this topic: Origins Of Baseball