Primary sources help you get as close as possible to what actually happened during an historical event or time period. A primary source reflects the viewpoint of a participant or observer.
Photographs, audio recordings and moving pictures or video recordings, documenting what happened.
Declaration of the German Republic, 9 November 1918 from the Digital Archive of the National Library of Scotland (no known copyright restrictions) via Flickr Commons
Materials that document the attitudes and popular thought of a historical time period. If you want to find evidence documenting the mentality or psychology of a time, or of a group (evidence of a world view, a set of attitudes, or the popular understanding of an event or condition), the most obvious source is public opinion polls taken at the time. Since these are generally very limited in availability and in what they reveal, however, it is also possible to make use of ideas and images conveyed in the mass media, and even in literature, film, popular fiction, textbooks, etc. Again, the point is to use these sources, written or produced at the time, as evidence of how people were thinking.
Research data such as anthropological field notes, the results of scientific experiments, and other scholarly activity of the time.
Artifacts of all kinds: physical objects, buildings, furniture, tools, appliances and household items, clothing, toys.
This bowl depicts President James Garfield and it is from the Susan H. Douglas Political Americana Collection, #2214 Rare & Manuscript Collections, Cornell University Library, Cornell University (no known copyright restrictions) via Flickr Commons