What's the history of the CIA? Why was it formed and what was the Central Intelligence Agency Act of 1949?

The Central Intelligence Agency was formed in 1947 to be
the central spy agency for the United States.  In previous years, there had been many
different intelligence agencies.  For example, the Army would have their intelligence
agency and the State Department would have theirs.  These agencies did not really talk
to one another.

In 1947, the Central Intelligence Agency
was formed to make sure that intelligence would be gathered and shared.  It was supposed
to make sure that there would not be any further lapses in intelligence like the one
that allowed the Japanese to attack Pearl Harbor without anyone realizing it was about
to happen.

Two years later the CIA expanded in power with
the Central
Intelligence Agency Act of 1949. This act permitted the agency to use methods
that would otherwise limit the organization from receiving federal funding. In other
words, the CIA was granted special powers and its veil of secrecy, as it was exempt from
disclosing information like its employees' names and salaries. This act was challenged
in 1972 with the court case href="http://en.wikipedia.org/wiki/United_States_v._Richardson">United States v.
Richardson but was ultimately upheld.