Complex sentence: In 1959, Veeck became head of a group that purchased a controlling interest in the Chicago White Sox, who went on to win their first pennant in 40 years, and broke a team attendance record for home games with 1.4 million.
Split into simpler sentences: In 1959, Veeck became head of a group that purchased a controlling interest in the Chicago White Sox, who went on to win their first pennant in 40 years. That year the White Sox broke a team attendance record for home games with 1.4 million.