Answer: Mind Control
Or, at least, attempted mind control. The project, code-named MKULTRA, began at the order of CIA director Allen Dulles in 1953. Some of MKULTRA's tests involved administering chemicals, such as LSD, to unwitting American and Canadian soldiers and citizens. A Congressional investigation took place in August, 1977 following the FOIA revelation.
Ironically, many of MKULTRA's volunteer subjects grew fond of taking LSD and would go on to start the hippie movement.