CIA

It has been working since the government of George Washington. But it was till WWII that made real things happen. It was first named OSS (Office of Strategic Services) in 1942. When WWII finished, this organization was eliminated and the problems they carried were passed to State and War Departments. In 1947 President Truman felt tat he needed an organization that will take care of the security of the people. It was called CIA. He signed the National Security Act.
For more info go to:

https://www.cia.gov/about-cia/history-of-the-cia/index.html