Northwestern's Izzy Scane scored six goals to reach her 60th of the season.
Despite a comeback effort, the Terrapins' five-goal lead in the second period proved to be too much to overcome.
The men's team sits at No. 10, while the women's team jumped to No. 20.
Gretchen Gilmore and Kristin O'Neill each scored six goals in the upset win for Penn State.
With six games left in the regular season, Penn State must continue to share the wealth on offense and win face-offs.
Towson held Kristin O'Neill to two goals from nine shots.