Complex sentence: In its 12-year history as an amateur league, the Brooklyn Atlantics won seven championships, establishing themselves as the first true dynasty in the sport, although the New York Mutuals were widely considered to be one of the best teams of the era as well.
Split into simpler sentences: In its 12-year history as an amateur league, the Brooklyn Atlantics won seven championships, establishing themselves as the first true dynasty in the sport, although. The New York Mutuals were widely considered to be one of the best teams of the era as well.