Original materials that provide direct evidence or first-hand testimony concerning a topic or event.
Primary sources can be contemporary sources created at the time when the event occurred (e.g., letters and newspaper articles) or later (such as, memoirs and oral history interviews).
Primary sources may be published or unpublished. Unpublished sources are unique materials (e.g., family papers) often referred to as archives and manuscripts.
What constitutes a primary source varies by discipline. How the researcher uses the source generally determines whether it is a primary source or not.
2) Secondary Sources
Works that interpret, analyze, and discuss the evidence provided by primary sources (e.g., scholarly books and articles).
Secondary sources are generally a second-hand account or observation at least one step removed from the event.
Secondary sources, however, can be considered to be primary sources depending on the context of their use. For example, Ken Burns' documentary of the Civil War is a secondary source for Civil War researchers, but a primary source for those studying documentary filmmaking.
3) Tertiary Sources
Books or articles that synthesize or distill primary and secondary sources, often in a convenient, easy-to-read form (e.g., dictionaries, encyclopedias, indexes, and textbooks).
