Material in archives is often arranged by the creator of the materials - who or what entity/office created them - because the context surrounding the records is often just as important as what the individual materials in the collection say.
This is important because your research topic could be in different collections across the University Archives.
Archival materials are usually described using a Finding Aid.
Findings aids are sort of like a mix between a Wikipedia entry and a library record. It's a tool that facilitates discovery of information within a collection of records, places the material in context, and typically includes:
Often unique materials that are not duplicated elsewhere.
Records in a variety of formats, including
Handwritten, typewritten and printed documents;
Photographic negatives, prints, and slides;
Motion picture film, audio and video tape;
Architectural plans and blueprints;
Oral history tapes and transcripts;
Scrapbooks, artifacts, and ephemera; and
Digital files (many formats: docx, PDF, mp4, etc.)
Generally, a mixture of primary and secondary sources
Records documenting the business of the University with long term administrative, legal, financial, or historical value
University publications, handbooks, catalogs and bulletins, and commencement and athletic programs,
Student publications including the Marquette Journal, the Hilltop yearbook, and the Marquette Tribune
Publications by faculty, staff, and alumni
Copies of graduate essays, theses, and dissertations
Personal and professional papers of faculty; organizational records of student groups; papers, photographs, and memorabilia
Secondary sources about the history of the university
Approximately 5,000 cubic feet of material from the 1800s to the present!