While a huge amount of primary source material is still buried in archival backlogs or stored behind paywalls, advances in digitization and hosting technology means more than ever before in history, primary resources are only a few keystrokes away.
For citation guidelines, see:
Chicago: https://www.loc.gov/programs/teachers/getting-started-with-primary-sources/citing/chicago/
MLA: https://www.loc.gov/programs/teachers/getting-started-with-primary-sources/citing/mla/