California, Washington, Florida and Texas have the most claimed UFO sightings. The National UFO Center counts 11,277 unidentified flying object reports for California as of May 2015. Florida has 5,201 reports, while Washington and Texas have 5,042 and 4,395, respectively.
The National UFO Center's reports for California date back to 1935 when a cluster of three bright lights in a triangular formation were observed over Covina, California. The object made rapid vertical ascents and descents over a five-minute period before disappearing.
California reports also include the Great Los Angeles Air Raid of 1942. On the night of Feb. 24, 1942, at the onset of World War II, an air raid siren sounded throughout Los Angeles County and a total blackout was ordered. The U.S. military fired anti-aircraft artillery at suspected Japanese forces. The event was quickly reported as a false alarm by the U.S. Navy. In 1983 the U.S. Air Force commented on the event and placed blame on war nerves and a possible lost weather balloon. Some sceptics believe the target was an extraterrestrial spacecraft.
One of the earliest reported UFO sightings in the United States was on Feb. 28, 1904. Three bright red egg-shaped objects were observed 300 miles west of the San Francisco coast by three crew members aboard the U.S.S. Supply. The three objects flew in echelon formation just below the cloud layer. The event was reported a few days later in the New York Times and the Richland Shield and Banner newspaper.