The Central Intelligence Agency (CIA) is a civilian foreign intelligence service of the United States federal government, tasked with gathering, processing, and analyzing national security information from around the world.

The National Resources Division is the domestic wing of the CIA. Although the CIA is focused on gathering intelligence from foreign nations, it has performed operations within the United States to achieve its goals. Some of these operations only became known to the public years after they had been conducted, and were met with significant criticism from the population as a whole, with allegations that these operations may violate the Constitution. 

1950

Starting in 1950, the CIA researched and experimented with the use of possible mind-control drugs and other chemical, biological and radiological stimuli on both willing and uninformed subjects. The purpose of these programs was to "investigate whether and how it was possible to modify an individual's behavior by covert means."[6]

CIA Director Roscoe H. Hillenkoetter approved the first mind-control study, named Project BLUEBIRD, which was later renamed Project ARTICHOKE.[7]
Crusade for Freedom
Main article: Crusade for Freedom

1950 was the beginning of the Crusade for Freedom, a ten-year campaign to generate domestic support for Radio Free Europe (and to conceal the CIA as the primary source of RFE's funding).[8]
Project MK-ULTRA
Main article: Project MKUltra

Project MKULTRA was a CIA program which involved, among other projects, research on the use of drugs in behavior modification.[9] One of the most controversial cases arising from the program was the death of Dr. Frank Olson, a scientist who worked in the Special Operations Division of the U.S. Army Biological Center in Camp Detrick, Maryland.[10] According to the Church Committee, as part of the MK-ULTRA experiments, Olson was given a dose of LSD without his knowledge, and eventually suffered a severe psychiatric response. The CIA sent him to New York to see one of their psychiatrists, who recommended that Olson be placed into a mental institution for recovery. While spending the evening in a hotel room with another CIA employee, Olson threw himself out his hotel room window, plunging to his death.[11] Olson's family members have contested this account.Later forensic evidence conflicted with the official version of events; when Olson's body was exhumed in 1994, cranial injuries indicated that Olson had been knocked unconscious before he exited the window.[12] 

1951
Forerunner of Domestic Contact Service/OSINT

This function, run by the Domestic Contact Service (also called the Domestic Contact Division) of the CIA, was legal, as it did not violate the CIA prohibitions of police power or spying on Americans. It was a voluntary debriefing of Americans with useful information. It is now considered part of Open Source Intelligence OSINT.[13]
Office of Current Intelligence
President Truman created the Office of Current Intelligence[14] which was directed by Huntington D. Sheldon. This was a renamed and extended version of the World War II section of the OSS that gave White House and other high-level briefings.