Delta Upsilon (ΔΥ), commonly known as DU, is a collegiate men's fraternity founded on November 4, 1834 at Williams College in Williamstown, Massachusetts. It is the sixth-oldest, all-male, college Greek-letter organization founded in North America (only Kappa Alpha Society, Sigma Phi, Delta Phi, Alpha Delta Phi, and Psi Upsilon predate). It is popularly and informally known as "DU" or "Delta U" and its members are called "DUs". Although historically found on the campuses of small New England private universities, Delta Upsilon currently has 76 chapters/colonies across the United States and Canada. A number of its buildings are listed on the National Register of Historic Places.