Now is a great time to be researching history! Every day, more and more content that was previously accessible only in special collections and archives is now being scanned, digitized, and posted on the web.
Search for primary source documents both online and in the library catalog, Library Search.
Search Library Search to find books containing primary source resources.
Try adding one of the following words to your search to find collections of the kinds of primary sources you are looking for:
"Documents"
"Sources"
"Personal Narratives"
"Correspondence"
"Diaries"
"Speeches"
"Pamphlets"
e.g., "Korean War AND Sources"
"Civil War AND Sources"
Search Library Search to find books by a particular person using the "Advanced Keyword Search" author field, e.g. "Voltaire, 1694-1778." You might also want to limit the language to "English".
Books published before 1930 are in the Public Domain, so the full-text of many historical books may be found via Google Book Search.