Basic Readings in U.S. Democracy - Court decisions, legislative acts, presidential decrees, letters, essays, surrender speeches and even poems chosen for their significance in the development of American democracy.
Immigration to the US.1789-1930 - Organized around broad topics, this site provides short summaries followed by a selection of relevant primary documents.
Foreign Relations of the United States - From the Office of the Historian of the US State Department, this collection documents America's foreign policy decisions and significant diplomatic activity 1945-1976. It can be searched by administration, title, or dated chapter.
CIA Historical Collections - Declassified intelligence documents organized in themes - for example, "Bosnia, Intelligence, and the Clinton Presidency", "CIA Analysis of the Warsaw Pact Forces" or "Bay of Pigs release". Note: some redactions.