Primary sources are evidence that date from the time period being studied, immediate to the events under investigation. There are many kinds of evidence, written, material, or visual, physical or electronic, and so on. For instance:
Reading secondary sources carefully to mine the primary sources that scholars have already cited is also an excellent method of learning about primary sources in a particular historical field or those being used to answer certain historical questions. Using any of the terms above, or their synonyms, may aid in searching for primary sources to discover them through library catalogs, indexes, databases, websites, etc.
The usual subheading for primary sources in library catalogs is “sources”. Sample subject headings include:
France -- History -- Revolution, 1789-1799 -- Sources
Soviet Union -- History -- Revolution, 1917-1921 -- Sources
United States -- History -- Civil War, 1861-1865 -- Sources
See the following for an overview on doing archival research: