Primary sources are the raw materials of history - original documents and objects which were created at the time under study. They are different from secondary sources, accounts or interpretations of events created by someone without firsthand experience.
The collections below are rich sources of primary material but this is not an exhaustive list of primary materials held in the library. Use Primo to search for published letters, diaries, household accounts, wills, inventories, records, etc. Try using the type of material you hope to find as part of your Primo search term.
There are many useful primary sources freely available on the internet but do be mindful of who is responsible for producing these resources.