Letters from relatives and friends of Mildred J. Leigh along with a few copies of her outgoing messages. Among the letters are: one written by an ancestor, Albert Smith, who served in Company F, 86th Illinois Infantry, at Gordon's Mill, Georgia on April 11, 1864; items from Gentle, Smith, and Leigh ancestors writing family members from various locations in New Mexico, Illinois and Iowa during the nineteenth and early twentieth centuries; several notes from Edward P. Eardley of Salt Lake City to Marjorie Ann Leigh during the 1930s; reports from service men acquainted with the Leigh sisters serving during World War II; extensive items from former Montana State College librarian Lois Payson to Mildred J. Leigh; extensive items from Marjorie Ann Leigh to Mildred J. Leigh prior to Marjorie's residence in Montana in the late 1960s. The letters have been chronologically arranged with the exception of the holiday greeting letters from Montana State College extension agent Harriette Cushman which have been placed in a separate file.

Written essays, legal documents, and other material collected by Mildred J. Leigh over her lifetime. Subjects include the genealogy and family history of the Leigh, Gentle, and Smith families in Illinois and elsewhere, Mildred J. Leigh's career at Montana State University, the meetings and transactions of the Montana Institute of the Arts Bozeman History Group chapter, and obituaries and essays written by Mildred J. Leigh and others on named individuals associated with Montana State University.

Loose photographs and thematic photograph albums containing images of Mildred J. Leigh, Marjorie Ann Leigh, students and staff of Montana State College and University, and the various extended members of the Gentle, Smith, and Leigh families of Illinois. The photographs have been sequentially numbered and placed in topically labeled files.