The use of primary sources is central to the study of history and the process of conducting historical research. Primary (also known as original) sources come in many forms, including artifacts, documents, diaries, correspondence, manuscripts, autobiographies, photographs, newspaper articles, etc. By definition, a primary source was either created during the time period being studied, or at a later date by a participant, or eyewitness to the events being studied.
Founders Online, launched by the National Archives in 2010, features over 180,000 historical documents in chronicling America's founding era.