Primary sources can be very important in doing historical research. These are documents of many kinds which were created during the period you are studying -- personal accounts like letters and diaries, newspapers, magazines & journals, books, government documents, and much more.
There is a separate guide to United States Historical Newspapers, and a Guide to Online Primary Sources that includes all kinds of primary sources in all subject areas. This guide is the US History subsection of that guide. To see more specific types of primary sources, mouse over the "Primary Sources" tab at the top of this page and look at the sections on personal accounts, historical texts, and primary source collections.
Primary sources are extremely important for historical research. They can be materials produced during the period you are researching: newspapers, other periodicals, even books, as well as letters, diaries, government publications and much more. There is a separate guide to U.S. Historical Newspapers and a separate Guide to Online Primary Sources in all periods of history. This page gives you a selection of primary sources selected for their value to research in U.S. History.