You can search the library catalog for books that contain primary sources. Some subject terms to use are:
6. History Sources
7. Civilization Sources
Try putting your topic term in the Words or Phrase field and then put the term Sources in the Subject field.
The Internet Archive also contains digital books.
Also check Google Books for digital sources.
Another collection of primary source documents is found in the series "The Library of Original Sources" edited by Oliver J. Thatcher.
From the preface: "It is the purpose of this work to present the ideas that have influenced civilization in the words of the men or the documents that developed them."
Unfortunately the Salmon Library no longer has the complete set. But these volumes may help your research project.
All the volumes are available as PDF files at the Internet Archive.
This is not an inclusive list but some suggested SUBJECT search terms:
You can also add the name of a county to the search term:
Example: China History Sources