After being experimented on for nearly a decade, MonKey ULTRA was named after Project MKUltra, the CIA's (at times illegal) mind control program using hallucinogenic drugs, most notably LSD 25. The CIA underestimated the consciousnesses expanding power of these substances though, and after the initial tests MonKey ULTRA started to develop complex thoughts about who and what exactly he was in the universe.
The CIA continued to train him to do their bidding for years, until he had developed enough mental capability to rival even the smartest minds, including his gatekeeper which he was able to put into a state of psychedelic hypnosis and escape the compound.
He did not leave empty handed though and stole a box of files containing documentation of the history and results of the experiments. After Gerald Ford issued an investigation into the CIA's activities, the CIA attempted to cover up the entire project and ordered all files be destroyed. However the single stolen box was released to the public in 1977 due to The Freedom of Information Act and is the only evidence remaining.