Primary sources provide first-hand testimony or direct evidence concerning your topic. Often these materials are created at the time when the events or conditions are occurring, but they can also include autobiographies, memoirs, and oral histories recorded later.
In the humanities, primary sources are most often "original works--diaries, letters, manuscripts, images, films, film scripts, recordings, and musical scores created by writers, artists, composers, and so on. Those sources provide data--the words, images, and sounds that you use as evidence to support your reasons. Data can also be objects: coins, clothing, tools, and other artifacts from the period or belonging to a person you're studying." (Turabian, A Manual for Writers of Research Papers, Theses, and Dissertations)
Primary sources are characterized by their content, regardless of whether they are available in their original format, in microfilm/microfiche, in print or digital format. At Rutgers, you will find primary source material in most of our libraries, however most of it is held in Special Collections and University Archives (SC/UA) at Alexander Library. Many, but not all of their items are in the library catalog.
You can search for SC/UA materials by doing either a basic (keyword) or advanced search, then using the filters on the left-hand side of the page to limit by Library (Special Collections-University Archives) and by Resource Type (books, maps, etc.). Please note that archival collections may be found under "manuscripts," "archival collections," and "other" (select all three checkboxes). See the Special Collections and University Archives website for access to collections in the form of archival finding aids.