Women have represented about 57 percent of American college students since 2000 according to the American Council on Education.
At the University of North Carolina, Chapel Hill, the student body that is nearly 60 percent female.  According to an article in The New York Times, the gender imbalance is also pronounced at some private colleges, such as New York University, College of Charleston in South Carolina and Lewis & Clark in Portland, Oregon as well as at a number of large public universities in California, Florida, Vermont and Georgia.
The New York Times cites several reasons for the gender gap: women tend to have higher grades; men tend to drop out in disproportionate numbers; and female enrollment skews higher among older students, low-income students, and black and Hispanic students.
According to the Times, the gender gap is not universal.  In fact at most Ivy League schools man and women comprise a near equal representation.