The Theta Rho chapter of the Delta Delta Delta sorority was established at The University of Montana in 1926. After forty-five years of campus and community involvement and service, the chapter was disbanded in 1971, when interest in the Greek system lagged. In the best philanthropic tradition, TriDelta alumnae placed chapter assets in a specially crafted trust that made the University's Maureen and Mike Mansfield Library the Trust's primary beneficiary.

Thanks to the foresight and vision of the women of the Theta Rho chapter, The Delta Delta Delta Theta Rho Library fund continues to support the needs of the Maureen and Mike Mansfield Library, including the purchase of library materials and equipment, the maintenance of collections, and support for special projects. Theta Rho TriDelta members, who are located across North America, continue to maintain a keen interest the development of the collections and services of the Maureen and Mike Mansfield Library.