The government destroyed most of the MKUltra records in 1973, but thousands of misfiled documents were later discovered.

In 1973, the head of the CIA ordered all MKUltra files destroyed to keep them secret. They thought the truth was gone forever. But in 1977, investigators found seven boxes of financial records that had been misfiled in a different building. These papers proved the CIA had funded 149 different subprojects. This discovery forced the government to admit the truth in public Senate hearings, revealing the massive scale of the experiments.