Chronologically: 1750 - 1899
The American Civil War Home Page Links to hundreds of resources, including timelines, overviews, images, letters, accounts and diaries, bibliographies, state studies, specific battles and rosters. A good place to start any search for Civil War information.
American Civil War Resources: Civil War materials from the Digital Library & Archives, Virginia Tech Libraries containing letters and diaries from both Union and Confederate soldiers, homefront letters, memoirs, and contemporary research files.
Congressional Documents: A Century of Lawmaking, 1774 - 1875: One of the major collections in the American Memory website, this invaluable (but hard to find) site includes all major congressional documents for the country's first century. The four main categories are: The Continental Congress and the Constitutional Convention; Journals of Congress; Debates of Congress; and States and Documents.
Documenting the American South A collection of sources on Southern history, literature and culture from the colonial period through the first decades of the 20th century. Provides access to digitized primary materials that offer Southern perspectives on American history and culture.
Liberty and the American Revolution The Sid Lapidus '59 Collection on Liberty and the American Revolution features more than 150 recently gifted important books, pamphlets and prints representing the major themes of Lapidus' collecting: the intellectual origins of the American Revolution; the Revolution itself; the early years of the republic; the resulting spread of democratic ideas in the Atlantic world; and the effort to abolish the slave trade in both Great Britain and the United States.
Making of America(Cornell University); Making of America( University of Michigan)
(1800-1925 ) Full text of primary sources in American social history from the antebellum period through reconstruction. Particularly strong in the subject areas of education, psychology, American history, sociology, religion, and science and technology. This is actually two separate sites with separate resources -- one site is sponsored by The University of Michigan and the other by Cornell University.
The U.S. Civil War Center (Louisiana State University) A collection of web links to indexes, letters, diaries, museums, discussion groups, newspapers, university archives, and Web-accessible documents. The 'historic places' portion leads to information on battlefields, cemeteries, forts, and historic sites.
The War of the Rebellion: Both The War of the Rebellion: a Compilation of the Official Records of the Union and Confederate Armies (1880 - 1901) and the Official Records of the Union and Confederate Navies in the War of the Rebellion (1894 - 1922) are available full text online at Cornell University's Making of America site. These are obviously two of the most significant civil war resources.
Chronologically: 1900 - 1949
Franklin D. Roosevelt Library Digital Archives: A growing body of presidential and personal papers related to the FDR presidency. Included are the President's Secretary File(PSF); British & German Diplomatic files; US-Vatican Diplomatic files, Fireside chats; and the Hackett Papers.
The Holocaust History Project: The Holocaust History Project is a free archive of documents, photographs, recordings, and essays regarding the Holocaust, including direct refutation of Holocaust-denial.
HyperWar: A Hypertext history of the Second World War "This project is a collection of material related to the (primarily military) history of the Second World War, completely cross-referenced via hypertext links and enhanced, where appropriate, by various multi-media computer technologies."
"Let there be Light" ( John Huston 1946 WWII film): John Huston’s World War II documentary Let There Be Light is so legendary for its censorship controversy that its sheer power as a film has been easy to miss. Produced by the U.S. Army in 1945, it pioneered unscripted interview techniques to take an unprecedented look into the psychological wounds of war.
The Modernist Journals Project The MJP is a multi-faceted project that aims to be a major resource for the study of modernism and its rise in the English-speaking world, with periodical literature as its central concern. The historical scope of the project has a chronological range of 1890 to 1922 (though the earliest journals that currently appear on the site date from 1896 and 1904), and a geographical range that extends to wherever English language periodicals were published.
World War I Document Archive: This archive of primary documents from World War I has been assembled by volunteers of the World War I Military History List (WWI-L). The archive is international in focus and intends to present in one location primary documents concerning the Great War. Also worth looking at is: World War I: Trenches on the Web.
World War II Resources "Primary source materials on the Web"
Civil Rights Documentation Project - A Mississippi site which includes transcripts of oral history interviews, a civil rights timeline, and bibliography.
Free Speech Movement Archives. The link takes you directly to a list of pages and primary sources documenting the Free Speech Movement at Berkeley. This is the only way to get an idea of the extent and scope of this site's holdings.
Macmillan Cabinet Papers, 1957 - 1963: Provides historians and political scientists withdirect access to documents from the highest level of Government during the Macmillan Administration. Contains 30,000 original documents, as well as five essays on the Macmillan Administration.
National Security Archive An independent non-governmental research institute and library located at The George Washington University, the Archive collects and publishes declassified documents obtained through the Freedom of Information Act. The Archive also serves as a repository of government records on a wide range of topics pertaining to the national security, foreign, intelligence, and economic policies of the United States.
The Vietnam Archive "The Vietnam Archive mission is to collect and preserve the documentary record of the Vietnam War.... The Vietnam Archive currently administers two projects, the Oral History Project and the Virtual Vietnam Archive. More information about both of these project can be found in their respective sections of this website."
Yahoo - U. S. History The 1960's
The first place to start for a search of Internet sites for U. S. History. Particularly useful for tracking down sites with primary sources. Its hierarchical arrangement is as close to a library as one gets on the web. The 1960's page contains individual website links as well as the following categories: 1960 Presidential Election; 1964 Presidential Election; Baby Boomers; Civil Rights Movement; Cuban Missile Crisis; Hippies; and Vietnam War.