Here's what William Cooper (author of Behold a Pale Horse) has to say about why C_A was formed. Don't panic, as you dig deeper this shit can be clarified.
>"An alien craft was found on February 13, 1948, on a mesa near Aztec, New Mexico. Another craft was located on March 25, 1948, in White Sands Proving Ground. It was 100 feet in diameter. A total of 17 alien bodies were recovered from those two crafts. Of even greater significance was the discovery of a large number of human body parts stored within both of these vehicles. A demon had reared its head and paranoia quickly took hold of everyone then "in the know." The Secret lid immediately became a Top Secret lid and was screwed down tight. The security blanket was even tighter than that imposed upon the Manhattan Project. In the coming years these events were to become the most closely guarded secrets in the history of the world. A special group of America's top scientists were organized under the name Project SIGN in December 1947 to study the phenomenon. The whole nasty business was contained. Project SIGN evolved into Project GRUDGE in December 1948. A low-level collection and disinformation project named BLUE BOOK was formed under GRUDGE. Sixteen volumes were to come out of GRUDGE. "Blue Teams" were put together to recover the crashed disks and dead or live aliens. The Blue Teams were later to evolve into Alpha Teams under Project POUNCE. During these early years the United States Air Force and the Central intelligence Agency exercised complete control over the "alien secret." In fact, the CIA was formed by Presidential Executive Order first as the Central Intelligence Group for the express purpose of dealing with the alien presence. Later the National Security Act was passed, establishing it as the Central Intelligence Agency. "