Google is a wonderful tool for finding Primary sources just be careful how you use it. Use the advanced search in Google, it allows you to limit your results by domain such as .edu, .org or .gov resources.
Try searching for your topic plus terms like "Primary Sources", letters, diaries or "digital collections" to find collections of digitized materials at museums, historical societies, colleges and universities.
Happy and smart Googling!
Primary materials are available in many different places. The library has database subscriptions to primary source materials including newspapers, diaries, letters, etc. Primary sources might also be found reproduced or transcribed in secondary sources. Also many libraries and other organizations such as historical societies are placing digitized images of archival (primary source) materials online.
Keep in mind when searching for primary sources that the language used at the time might be different than what is used today and may also vary by region. Example: The Civil War may be called The War of Northern Aggression or The War of the Rebellion.
Helpful Primary Source Subject Headings:
Add these to the end of any useful Subject Headings you find and do a new search.
--Correspondence
--Personal Narratives
--Maps
Ex: Searching United States History--War of 1812--Correspondence will give you results for primary sources like letters during the War of 1812.
The link below will help you find primary and secondary sources for your history papers.