The Knickerbocker Base Ball Club was one of the first organized baseball clubs in the United States, founded in 1845 in New York City. It played a significant role in the development of modern baseball rules, including the establishment of nine-player teams and the use of bases. The club's founder, Alexander Cartwright, is often credited with formalizing the game and promoting its growth. The Knickerbockers played their first official game on June 19, 1846, against the New York Nine. Their influence helped popularize baseball, leading to the formation of other clubs and the eventual establishment of professional leagues. The club's legacy continues to be recognized in the history of American sports.