There are different types of primary sources. One way to search is using a genre keyword + your topic keyword(s).
For first-person evidence, try using:
For lists or statistics, try:
Example searches:
For archival collections, use a finding aid repository like
For digital surrogates of archival materials (like historical photos, or scans of letters or diaries), use a digital primary source repository like
For books that have been mass-digitized (most materials currently in the public domain, pre-1925), try