The fourth-oldest college in the United States, Princeton University retained its No. 6 ranking from last year. Established in 1746 as the "College of New Jersey," the university now enrolls about 5,000 undergraduates and 2,500 graduate students. The institution counts more than 30 Nobel laureates among its past faculty and alumni, and its Nassau Hall hosted meetings of the Continental Congress in the spring and fall of 1783.

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Some people take cover from a light rain during Princeton University's Class Day ceremonies June 3, 2013 in Princeton, NJ.