Adelphi University is a private, nonsectarian university located in Garden City, in Nassau County, New York, United States. Adelphi also has Centers in Manhattan, Hudson Valley, and Suffolk County. It is the oldest institution of higher education on Long Island. For the sixth year, Adelphi University has been named a "Best Buy" in higher education by the Fiske Guide to Colleges. The university was also named a 2010 Best College in the Northeastern Region by The Princeton Review. The institution was awarded the 2010 Carnegie Classification for Community Engagement by the Carnegie Foundation for the Advancement of Teaching. U.S.