Primary sources are information or evidence contemporary to the event or topic under investigation. These are sources created during an historic event, usually by an eyewitness. Primary sources are generally one of a kind and they are not published documents. Examples of primary sources found in manuscript collections include letters, diaries, photographs, account books, minutes of meetings, scrapbooks, etc.
Written descriptions of an event that are based on primary sources are considered secondary. These include research papers, text books, historical monographs, and other published works. Before researchers start looking for primary sources, they must read relevant secondary sources about the topic to become familiar with the individuals involved, the places, the dates, and the actions that transpired to shape an historical event. Once researchers know these facts they are better prepared to explore and interpret evidence found in primary sources.
The difference between primary and secondary sources is not always distinct. A primary source for one topic, may be secondary for another. Always keep in mind when the document was created, by whom, and for what purpose. For example, a newspaper article written by a correspondant who witnessed the Battle of Wilson's Creek in 1861 is considered a primary source for a researcher studying the Civil War. A newspaper article written by an historian in 2001 about the same battle is considered a secondary source. Both sources are newspapers, but the 1861 article was written by an eye witness of the battle; thus, it is considered a primay source.