Complex sentence: Hepburn Hall, built in 1905, was the first women's dorm at the college; by 1907, the enrollment at the University passed 700 students and women made up about a third of the student body.
Split into simpler sentences: Hepburn Hall, built in 1905, was the first women's dorm at the college. By 1907, the enrollment at the University passed 700 students and women made up about a third of the student body.