A Timeline of U.S. UFO Investigations: From Project Sign to Project Blue Book (1947–1969)

To the point

From 1947 to 1969 the United States studied unidentified flying objects through Sign, Grudge, and Blue Book, moving from early extraterrestrial speculation led by Kenneth Arnold and General Hoyt Vandenberg to a systematic, skeptical analysis guided by Edward J. Ruppelt, with the Robertson Panel and Edward Condon ultimately ending the program and leaving a cautious, enduring framework for examining the unknown.