A secret Central Intelligence Agency mind control program. National Security Agency spy operations aimed at Martin Luther King Jr. and Muhammad Ali. A federal manual for political assassinations.

It's not just the stuff of spy novels. It's also part of the daily work of the National Security Archive, which is turning 40.

The archive, a self-described group of "activist archivists," is not a government agency and collects declassified documents acquired through the Freedom of Information Act and other sources. Since its founding in 1985, the group has uncovered some of the nation’s darkest secrets, including transcripts of top U.S. officials discussing covert operations and memos from spy masters.

"These documents reveal what was done in the name of the American people but without their knowledge," Peter Korbluh, an analyst with the group since 1986, told USA TODAY. "These declassified documents are the currency of history. They contain the words, positions and operations of foreign policy actors of the United States of America and often they contain summaries of operations in other countries that are the only documentation of what happened there, so they will remain forever invaluable."