The predecessor to the National Security Council was the National Intelligence Authority (NIA) which was established by President Harry S. Truman's Executive Letter of 22 January 1946 to oversee the Central Intelligence Group, the CIA's predecessor. The NIA was composed of the Secretary of State, Secretary of War, Secretary of the Navy, and the Chief of Staff to the Commander in Chief.
The National Security Council was created in 1947 by the National Security Act. It was created because policymakers felt that the diplomacy of the State Department was no longer adequate to contain the USSR in light of the tension between the Soviet Union and the United States. The intent was to ensure coordination and concurrence among the Army, Marine Corps, Navy, Air Force and other instruments of national security policy such as the Central Intelligence Agency (CIA), also created in the National Security Act. In 2004, the position of Director of National Intelligence (DNI) was created, taking over the responsibilities previously held by the head of CIA, the Director of Central Intelligence, as a cabinet-level position to oversee and coordinate activities of the Intelligence Community.
On May 26, 2009, President Barack Obama merged the White House staff supporting the Homeland Security Council (HSC) and the National Security Council into one National Security Staff (NSS). The HSC and NSC each continue to exist by statute as bodies supporting the President. The name of the staff organization was changed back to National Security Council Staff in 2014.
On January 29, 2017, President Donald Trump restructured the Principals Committee (a subset of the full National Security Council), while at the same time altering the attendance of the Chairman of the Joint Chiefs of Staff and Director of National Intelligence. On April 5, 2017, President Trump removed Steve Bannon from the Security Council.
According to a National Security Presidential Memorandum 2, the Chairman of the Joint Chiefs of Staff and Director of National Intelligence were to sit on the Principals Committee as and when matters pertaining to them arise, but will remain part of the full National Security Council. However, Chief of Staff Reince Priebus clarified the next day that they still are invited to attend meetings. With National Security Presidential Memorandum 4 in April 2017, the Director of National Intelligence and the Chairman of the Joint Chiefs of Staff “shall” attend Principals Committee meetings and included the Director of the Central Intelligence Agency as a regular attendee. The reorganization also placed the Administrator of the United States Agency for International Development as a permanent member of the Deputies Committee, winning moderate praise.
As of 6 April 2017, the White House Chief Strategist has been removed from the National Security Council and the roles of the director of national intelligence, CIA director and chairman of the Joint Chiefs of Staff have been restored to the Principal's Committee.
For a detailed history of the United States National Security Council by year see: