In the study of history, a primary source is something that dates back to the time period when the event occurred. It could be:
To look for primary sources in books at our library, use the catalog's Advanced search mode and include "sources" in the Subject field as one of your search terms.
Of special interest is the official War of the Rebellion series in the reference collection (REF E 464 .U6). It includes government reports and dispatches from the Sand Creek massacre written by the soldiers involved. Use the index volume to locate the proper series and volume, then look for the reports by date (arranged chronologically).
Use this checklist to determine if a source is appropriate:
Authority: Who wrote it? What credentials does s/he have? [PhD, affiliation with university]
Source: Where was it published? How was it selected for publication? [look at submission guidelines for evidence of peer review or other editorial processes]
Currency: When was it published? Has it appeared in other forms with/out revision?
Research: Are other sources cited in a bibliography/reference list? Are foot/endnotes used?
Bias: Is there an objective viewpoint? Is the author making assertions without documentation, or with questionable documentation? [e.g., her/his own work, crackpots]