 In 1985, Old Main was added to the National Register of Historic Places.Dedicated in February 1898, Old Main was originally all classrooms on the second and third floor, with an auditorium (the Assembly Hall) on the upper floor and a library on the lower level (which now houses the university's telephone service unit).In 1911, Theodore Roosevelt came to Arizona for the dedication of the Roosevelt Dam, and spoke on the steps of Old Main.