US archives once tended to be opened sooner than British, owing to long-standing US Freedom of Information (FOI) law.
But the reverse now obtains. The pace of release in the US slowed markedly after 9/11, FOI is part of the British system (at least for the present), and the US entirely lacks an equivalent to the British "30-year rule" - a cut-off date at which a file WILL be opened, unless there is good reason for extended closure. Moreover, Britain is phasing in a 20 year rule from 2013.
margaretthatcher.org has visited the major US archives and put online the most valuable documents for the study of Margaret Thatcher and keeps new releases under review.
The Reagan Library (1981-89)
Inevitably, the Reagan Library in Los Angeles is much the most important US source for the career of Margaret Thatcher. Unnoticed by the British press, many Thatcher documents were released early following a FOIA request by the Reagan Library & Museum itself. After a burst of early releases, the pace has slowed and archivists candidly admit that complete declassification of their holdings may be a full century away.
Reagan and Thatcher wrote hundreds of letters to each other during their shared time in office, fully one quarter of which are already open and available on this site. Several records of their face to face conversations ("memcons") are also open and present here, as well as telephone records ("telcons").
There is a mass of briefing documents and memoranda, all on line, including a near complete set of briefings for the President's meetings with the Prime Minister, prompt cards for their conversations and candid US assessments of the Falklands War.
The site also offers the text of President's Reagan's meetings with the Soviet leader Mikhail Gorbachev, almost all of which are open to the public but which have never previously been published on or off-line free to view; similarly their open correspondence. Meetings of the NSC will also be uploaded when they became available, as a handful already are.
The Carter Library (1977-81)
The Carter Library in Atlanta has a mass of Thatcher-related papers dating from 1977-81. Far fewer of its British files are open than in the case of the Reagan Library, though wholesale review of classified files for release is supposedly underway in Washington via a process known as RAC ("remote access capture"), a programme managed by the CIA which seems to have no end.
The files have been searched carefully and several dozen documents placed on line.
The Bush Library (1989-91)
The Library of George Bush Sr. in College Station, Texas quickly released significant material on the first Gulf War, 1990-91, then fell into a long period of near silence following 9/11. Declassification has now resumed on a significant scale and many Presidential memcons are now available, though often with material cut out ('redacted') in the case of MT.
Material from the files has been placed online.
The Ford Library (1975-77)
The Ford Library at Ann Arbor, Michigan, holds a few records of President Ford's dealings with Margaret Thatcher when she was Leader of the Opposition, including a record of their meeting in 1975.
"Britain is a tragedy", commented Henry Kissinger in an Oval Office meeting a few months before her visit.
US National Archives (1979-90)
The archives of the US Department of State are housed at the US National Archives in College Park, Maryland. Many relevant document have been released from the State Department's archives under US Freedom of Information law, including a mass of Falklands material. CIA material declassified under FOI is also available at College Park, via a database known as CREST.
Selections will be uploaded.