 Two properties built outside the district's period of significance of 1814 to 1867 were grandfathered from the 1965 National Register designation because they relate to the continued work of the Workingman's Institute, founded by geologist and philanthropist William Maclure in 1838.These buildings include the Workingmen's Institute, a three-story, brick Romanesque Revival building constructed in 1894, and Murphy Auditorium, built in 1913, a three-story, brick Neoclassical auditorium.In addition to historically significant resources, the district includes over one hundred noncontributing buildings and sites constructed outside the Harmonist-Owenite period of significance.