For a brief description of primary sources, try the Primary vs. Secondary Sources page in the Library Basics libguide.
BGSU has access to many research databases of primary source materials. Try these groups of databases!
"A 'manuscript collection' is a group of materials having a common source or a collection of materials formed around a person or family." (full description at Univ. of West Florida)
At BGSU, manuscript collections can be collections of an author's work with correspondence, manuscripts, and/or proofs in the collection (see the Browne Popular Culture Library's manuscript collections). They can also document a particular group's activities, a family's history, or other topics/subjects (see the Center for Archival Collections manuscript collections).
An abundance of primary source materials are available here at BGSU - on nearly every floor, in fact. Examples of primary source materials are listed below (follow links for details).
Since "primary source" can have different meanings for different disciplines and fields of study, any number of materials in the UL could be considered primary sources. Here are some examples listed by library/collection/floor:
Main floor
Curriculum Resource Center (CRC) - 2nd floor
Music Library and Sound Recordings Archives (ML/BSSA) - 3rd floor
Browne Popular Culture Library (BPCL) - 4th floor
Center for Archival Collections (CAC) - fifth floor