"Primary resources provide firsthand evidence of historical events. They are generally unpublished materials such as manuscripts, photographs, maps, artifacts, audio and video recordings, oral histories, postcards, and posters. In some instances, published materials can also be viewed as primary materials for the period in which they were written. In contrast, secondary materials, such as textbooks, synthesize and interpret primary materials."      

Source for the quote and more information available about primary sources was retrieved from the UCLA Institute on Primary Sources. 

The list of websites below contain many primary resources that are digital copies (surrogates) of the original documents, photos, or artifacts.