In 1947, a rancher in Roswell, New Mexico, discovered debris from a high-altitude balloon that had crashed. The military quickly moved in and confiscated the debris, claiming it was from a secret project. However, many people believe that the debris was actually from a UFO.
In the 1950s and 1960s, there were a number of UFO sightings that were investigated by the United States Air Force. However, the Air Force eventually dismissed these sightings as misidentifications of natural phenomena.
In 1974, the United States Congress held hearings on UFOs. However, the hearings did not produce any conclusive evidence of extraterrestrial activity.
In recent years, there have been a number of new claims about government cover-ups of alien evidence. However, none of these claims have been substantiated.
Ultimately, the question of whether or not the government is hiding alien evidence is a matter of belief. There is no definitive evidence to prove or disprove either side of the argument.