Complex sentence: The New York Knickerbockers were one of the first organized baseball teams, which played under a set of rules, similar to the game today, and was founded by Alexander Cartwright, the father of modern baseball.
Split into simpler sentences: The New York Knickerbockers were one of the first organized baseball teams, which played under a set of rules, similar to the game today. The team was founded by Alexander Cartwright, considered one of the original developers of modern baseball.