When searching in the Library Catalog do a keyword Boolean search and add the word “source” to your search. Example:
“Thomas Jefferson” and sources
Other keywords to try:
Library of American Civilization (LAC):
LAC is a collection of materials on microfiche relating to all aspects of American life. Included in this collection are biographies, fiction, letters, texts of public addresses, humor, songs, essays, guide books and count less other topics regarding life in America from the colonial era to World War I. Search for LAC documents in the library catalog and go to the Information Desk for help finding and viewing microfiche.
Some of the books in LAC can be read online (through Google Books & Project Gutenberg.) Quinnipac University has a nice list of what's available online, archived here, and listed alphabetically by author: http://www.terryballard.org/lac.html
Use KU WorldCat and limit to archival sources
The library has a subject page with all its databases that contain primary source documents.
These large county volumes have long formed the cornerstone of local historical and genealogical research. They are encyclopedic in scope and virtually limitless in their research possibilities.
Published in Philadelphia from 1728 through 1800, The Pennsylvania Gazette is considered The New York Times of the 18th century. It provides the reader with a first hand view of colonial America, the American Revolution and the New Republic, and offers important social, political and cultural perspectives of each of the periods.
A unique full-image archive of The Wall Street Journal with complete coverage from 1889-2012. Includes display and classified ads, editorial and commentary.