The Mississippiana Collection is a comprehensive collection of books about Mississippi, by and about Mississippians, and/or published in Mississippi. As such, it constitutes a vital resource for the study of Mississippi history and culture. These books can be accessed through the library catalog.

In addition to the Mississippiana book collection, the library subscribes to several serials (magazines, journals, newsletters, and numerous other professional and organizational publications) relating to Mississippi. McCain Library serves as a depository for Mississippi state documents. These items provide information on virtually every facet of state government and the economic, social, and cultural characteristics of the state. Many of these can be accessed via the library catalog or by asking the reference librarian. A map collection includes city, country, and state highway maps and various types of soil, mineral, drainage, topographic, nautical, historical, and specialty maps. They document Mississippi and the region from 1699 to the present. Vertical Files consisting primarily of newspaper clippings and pamphlets contain up-to-date information about the people, events, social issues, institutions, cities, and towns of Mississippi. Also included is historical information on a variety of subjects. The Mississippiana Collection maintains copies of telephone books for the entire state, and city directories for the state's major cities.