The concept of the Unidentified Flying Object (UFO), ostensibly the vehicle of choice for alien visitors from outer space, originated in the United States in the 1940s and, over the course of five decades, has attracted a sizable cult of adherents stimulated by the phenomenon's embodiment of both antigovernment social protest and romantic secular humanism.

The first mass sightings of UFOs in the United States came in 1896, when a number of people from California to the Midwest reported seeing mysterious aircraft. According to reports, these dirigible-like machines were cigar-shaped and featured a host of intense colored lights. Another wave of UFO sightings were reported in 1909 and 1910, and, during World War II, several Allied pilots claimed to have spotted glowing objects that paced their airplanes. A Gallup Poll taken in 1947, though, indicated that few Americans associated flying disks with extraterrestrial spaceships; by and...