Constructed in 1891 as the university's main library, Zimmerman currently houses the department of psychology, one of Wittenberg's most popular majors. Throughout the years, Zimmerman has undergone several transformations. In the 1920s, the library was running out of space, so the Zimmerman family added an addition to the building. The newer section, constructed in the same grey limestone and in the same style, includes three rectangular windows and a hexagonal tower. In 1957, when Weaver Chapel and Thomas Library were completed, Zimmerman was no longer needed as a library, so work began to transform it for the home economics department. A two-story brick addition to the rear of the structure was part of this conversion. Since the closing of the home economics department, Zimmerman Hall first housed the history department and currently houses the psychology department. Each year a number of students join with faculty members to conduct cutting-edge research in Zimmerman. Psychology students also have an opportunity to present their senior projects at an annual conference in Chicago.