Via the The Library of Congress "Primary sources are the raw materials of history-original documents and objects which were created at the time under study. They are different from secondary sources, accounts or interpretations of events created by someone without firsthand experience." via Teachinghistory.org "Primary sources are materials directly related to a topic by time or participation. These materials include letters, speeches, diaries, newspaper articles from the time, oral history interviews, documents, photographs, artifacts, or anything else that provides first hand accounts about a person or event." Further, this article goes on to explain and exemplify how , "some materials might be considered primary sources for one topic but not for another."
Primary sources are treasured for being as close as we can get to an historical event without actually being there. However, it's important to keep in mind that individually, without context or secondary analysis, they may be exaggerated, biased, inaccurate or even falsified. Critical analysis and evaluation is especially important.
From The Library of Congress
Making Sense of Evidence
About Primary Source Portals
Historical primary sources created prior to popular use of the internet must be "digitized", photographed and uploaded to a database which can be accessed via the web. Due to the vast collections held by National institutions, such as museums and libraries, only a fraction of their resources have been digitized; it is an ongoing process. Shared here are the digitized collections from the institutions where the original primary source exists, in addition to partner organizations, who aggregate and curate resources from multiple institutions for easier public access, in addition to special interest curated collections.
US Primary Source Collections
The Digital Public Library of America
The Digital Public Library of America (DPLA) is an all-digital library that aggregates metadata — or information describing an item — and thumbnails for millions of photographs, manuscripts, books, sounds, moving images, and more from libraries, archives, and museums across the United States
The Library of Congress is the largest library in the world, with millions of books, recordings, photographs, newspapers, maps and manuscripts in its collections. The Library is the main research arm of the U.S. Congress and the home of the U.S. Copyright Office
National Archives is the U.S. Government’s collection of documents, (firsthand facts, data, and evidence from letters, reports, notes, memos, photographs, and other primary sources), that records important events in American history.
Search the National Archives by historical period & document type
National Archives: 100 Documents that Shaped America