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Primary sources are created by individuals who participated in or witnessed an event and recorded that event during or immediately after the event.
A student activist during the war writing about protest activities has created a memoir. This would be a primary source because the information is based on her own involvement in the events she describes. Similarly, an antiwar speech is a primary source. So is the arrest record of student protesters. A newspaper editorial or article, reporting on a student demonstration is also a primary source.
Deeds, wills, court documents, military records, tax records, census records, diaries, journals, letters, account books, advertisements, newspapers, photographs, and maps are primary sources.
Secondary sources are created by someone who was either not present when the event occurred or removed from it in time. We use secondary sources for overview information, and to help familiarize ourselves with a topic and compare that topic with other events in history.
History books, encyclopedias, historical dictionaries, and academic articles are secondary sources.
For further explanation and source material see: U.S. History in Context