The records include UFO sightings and psychic experiments from the Stargate programme, which has long been of interest to conspiracy theorists.
The move came after lengthy efforts from freedom of information advocates and a lawsuit against the CIA.
The full archive is made up of almost 800,000 files.
They had previously only been accessible at the National Archives in Maryland.
The trove includes the papers of Henry Kissinger, who served as secretary of state under presidents Richard Nixon and Gerald Ford, as well as several hundred thousand pages of intelligence analysis and science research and development.
More @ bbc.com
You can search the docs here: https://www.cia.gov/library/readingroom/...am-archive
Stargate programme... I always knew it was real!