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What is a primary source?
A primary source is an original work that scholars analyze in order to produce insight. They are a key component of almost every kind of research project. These works can include works such as correspondence, diaries, fiction/poetry, data sets, news media, phenomena, artwork, patents, artifacts, illustrations, manuscripts, photographs, and ephemera (pamphlets, broadsides). It can also include some peer-reviewed journal articles that report original research, as is the case in the sciences.
This definition is from Carleton College's Lawrence McKinley Gould Library. It appears in an expanded form on their Primary Sources research guide.