Complex sentence: A total of 30 teams now play in the American League (AL) and National League (NL) (15 teams in each league), which operated as separate legal entities from 1901 and 1876 respectively.
Split into simpler sentences: A total of 30 teams now play in the American League (AL) and National League (NL), with 15 teams in each league. The AL and NL operated as separate legal entities from 1901 and 1876 respectively.