You can find some primary sources in books. Below is a list of relevant subject headings. When searching for these in the catalog, try adding "sources", "documents", "correspondence" or "letters" to your search.
Atkins Library has a number of old newspapers on microfilm. These may be challenging to use because they do not have an index. However, if you have a specific date or narrow date range, this will help you in using the newspapers on microfilm.
A repository for digital collections. Items in the public domain (works published before 1923) are freely accessible online.