Primary sources provide first-hand testimony or direct evidence on a subject. They are created by someone who experienced the period or event first hand. Because they are eye-witness accounts, many primary sources are created at the time the event occured, but recorded memories -- such as autobiographies, memories, and oral histories -- are also considered primary sources. For more examples see What are Primary Sources (Yale University)
A great place to find primary sources related to California.
American Memory Library of Congress
A great place to find primary sources related to U.S. History. Search by topic: Native American History, African American History, Immigration/American Expansion
DocsTeach is a collection of thousands of primary source documentson topics such as the Revolution and the new nation, the Civil War and Reconstruction, the Great Depression and World War II, and other topics from the National Archives.
Google Books includes old and new books, and many of the older books can be used as primary sources.
Try entering your search terms and limiting the publication date (for example, between 1800-1900).