National Archives - The home to thousands of government documents.
Library of Congress - The home to thousands of primary sources in multiple formats. Also links to Congress.gov, the home for legislative information.
The Gilder Lehrman Institute - A private organization that holds thousands of primary sources.
Digital History - Hundreds of primary sources organized by era and topic.
Abraham Lincoln Presidential Library - Presidential library of Abraham Lincoln
Herbert Hoover Library and Museum - Presidential library of Herbert Hoover
Franklin Roosevelt Library and Museum - Presidential library of Franklin Roosevelt
Truman Presidential Library and Museum - Presidential library of Harry Truman
Dwight Eisenhower Presidential Library and Museum - Presidential library of Dwight D. Eisenhower
Gerald Ford Presidential Library and Museum - Presidential library of Gerald Ford
Lyndon Johnson Presidential Library - Presidential library of Lyndon Johnson
John F. Kennedy Presidential Library and Museum - Presidential library of John F. Kennedy
Richard Nixon Presidential Library and Museum - Presidential library of Richard Nixon
Jimmy Carter Presidential Library and Museum - Presidential library of Jimmy Carter
Ronald Reagan Presidential Foundation and Institute - Presidential library of Ronald Reagan
George H.W. Bush Presidential Library Center - Presidential library of George H.W. Bush
Bill Clinton Presidential Library and Museum - Presidential library of Bill Clinton
George W. Bush Presidential Library and Museum - Presidential library of George W. Bush
The Avalon Project - A project of Yale Law School, the site has thousands of documents organized by historical era.
State Historical Museum of Iowa - Lots of Iowa history primary sources.
New York Library Archives and Manuscripts - Search archives for lots of full-text resources.
Smithsonian - The Smithsonian is the world's largest museum, education, and research complex.
The University of Chicago Special Collections - This library holds rare books, manuscripts, university archives and a special jazz archive.
L. Tom Perry Special Collections at Brigham Young University - This library has manuscripts, lectures, photographs, rare books and more pertaining to Mormonism, world history, literature, and more.
Manuscript Reading Room - LOC's Manuscript Reading Room includes special collections and research tools.
British Library - This library has books, journals, manuscripts, maps, stamps, music and more.
The Library of Trinity College Dublin - This library has the Book of Kells and other books.
The National Library of Ireland - This library has a special collection that features documents and manuscripts going back almost 1,000 years.
American Museum of Natural History - Find research projects and special collections.
A Selection of Web-Accessible Collections at Harvard University - This Harvard collection has daguerreotypes, botanical images from Eastern Asia, Chinese rubbings and more.
Smithsonian Folkways - This collection has archives on American singers, history makers and more.