Several of Carleton's older buildings have been listed on the National Register of Historic Places (NRHP). Willis Hall, the first building on campus, was constructed from 1869 to 1872. Originally the hall contained the men's dormitory, classrooms, library, and chapel. The building was gutted by fire in 1879, after which it was entirely rebuilt within the existing stone shell. The original front of the building became the rear entrance with the construction of Severance Hall in 1928. As new buildings were constructed, various academic departments cycled through the building. Beginning in 1954, Willis served as the college student union, until it was replaced in 1979 by the Sayles-Hill Student Center, a converted gymnasium. Willis Hall now houses the Economics, Political Science, and Educational Studies offices. The college's clock bell tower and the main college flagpole, along with the radio tower for KRLX, are located on the roof.