A list of several digital library projects is listed on Wikipedia. Below are a few major portals that help you access digitized primary sources.
Images and documents from cultural heritage institutions across Minnesota.
Note: Academic departments and disciplines define 'primary sources' differently. Check with your instructor if you aren't sure what counts as a primary source for a specific assignment.
With that being said, these are some general characteristics of primary sources:
Primary sources are increasingly available online as historical societies, museums, and other organizations digitize their primary source collections. Try adding the terms below to your online search:
Use the Libraries' WorldCat catalog (the main search box on the library homepage) to find primary sources. Just type in your usual search terms and add one of the terms listed below!
Books, pamphlets, essays, and broadsides published during the 18th century (1701-1800).
American magazines and journals published prior to 1900.
The National Archives provides Document Analysis Worksheets that you can use to better observe and analyze various types of primary sources (e.g., photos, written documents, artifacts, posters, maps, cartoons, videos, and sound recordings) that you are using in your research.