The exact evolution of the game of baseball is unknown before 1845. The
only trace of the exact game of baseball is the knickerbocker rules but those
can only be traced back until 1845. There were once two camps. One,
mostly English, asserted that baseball evolved from a game of English
origin, the other, almost entirely American, said that baseball was an
American invention (perhaps derived from another American game).
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.
Baseball Before 1845
All You Need Baseball