According to History.com, Albert Hoffman, a Swiss chemist, discovered the hallucinogenic effects of LSD.
Hoffman worked at a pharmaceutical research laboratory. He created LSD-25, a synthetic drug, in 1938, as research on the medicinal value of lysergic acid compounds. In 1943, he accidentally consumed some. He was tripping and didn’t understand it at first. He wrote his experience down in his lab notes:
“Last Friday, April 16, 1943, I was forced to interrupt my work in the laboratory in the middle of the afternoon amd proceed home, being affected by a remarkable restlessness, combined with a slight dizziness. At home I lay down and sank into a not unpleasant, intoxicated-like condition characterized by an extremely stimulated imagination. In a dreamlike state with eyes closed (I found the daylight to be unpleasantly glaring), I perceived an uninterrupted stream of fantastic pictures, extraordinary shapes with intense, kaleidoscopic play of colors.”
In order to confirm the experience, he took the drug on purpose. He published a report announcing the discovery, and the popular drug made its entry into the world. As far as records say, widespread use did not happen until the 60s. It was made illegal in 1965.