The Mahn Center for Archives and Special Collections at Alden Library, 5th floor, is the official archive of the university. There you will find files, photos, documents, and papers related to OU's people and places. Also scrapbooks, student publications, sports programs, and other memorabilia! Don't hesitate to go ask them if they have sources for your research.
Note they have limited hours, and their materials must be used in-house!
Mahn Center staff along with the Libraries' Digital Initiatives staff have done several digitizing projects that relate to the history of the University: