On December 9, 1965, thousands of people across six U.S. states and Ontario reported seeing a fireball streak across the afternoon sky. In Kecksburg, Pennsylvania, residents reported a crash in the nearby woods. U.S. military personnel arrived shortly thereafter, sealed off the area, and were allegedly seen later removing a large object in a flatbed truck.

Official statements the next day attributed the fireball and the crash to a mid-sized meteor and asserted that nothing had been recovered from the woods in Kecksburg. But over the years, witnesses who arrived on the scene before the military moved in have described seeing a bronze-colored, acorn-shaped object roughly the size of a VW Beetle bearing markings that resembled Egyptian hieroglyphics. Spectators claimed they’d been forcefully turned away by armed military personnel when they tried to approach the site for a better look, and stories circulated about Men in Black-style officials turning up at the homes of Kecksburg residents and warning them to keep quiet about what they saw.

The intrigue and conflicting accounts surrounding the Kecksburg incident have predictably spawned a number of theories, one of the most popular, of course, being that it was an alien spacecraft that landed in the woods that afternoon. Others posit that the object was a piece from a Russian satellite – in particular, the spacecraft Kosmos 96, which reentered earth’s atmosphere that same day following a failed attempt to reach Venus – a misfired missile, or a time-traveling Nazi aircraft.

A particularly sinister piece of the Kecksburg mystery is the plight of John Murphy, a reporter for local radio station WHJB, who was among the first to arrive on the scene and claimed to have taken photos of object. Barred from covering the military’s activities and noting the the investigation’s extreme security measures, Murphy became convinced a coverup was afoot. Determined to probe the matter further, he created a radio documentary titled “Object in the Woods,” in which he described what he saw that day and his subsequent attempts to investigate the crash. But before the piece was aired, government officials allegedly visited Murphy’s home and confiscated his photos. Sources familiar with the original documentary, including Murphy’s wife, stated that the subsequently aired version of “Object in the Woods” had been heavily edited and didn’t mention the mysterious object at all. Four years later Murphy was killed in an apparent hit-and-run accident while vacationing in California.

In 1990 the Kecksburg incident attracted the attention of the television show Unsolved Mysteries, who, upon arriving in Kecksburg, proceeded to construct a life-size replica of the so-called Space Acorn based on eyewitness accounts. Following the shoot, the prop was left in Kecksburg where it was eventually placed on an elevated platform on a prominent hill in the hopes of emulating the tourist draw surrounding the famous incident in Roswell. A UFO store peddling T-shirts, a documentary titled “Kecksburg: The Untold Story,” and replica street signs of the nearby Meteor Road (renamed in recognition of the crash) now operates across the street from the Space Acorn, adjacent to the bar in the fire department’s social hall.

Today the Space Acorn continues to attract visitors to the small Pennsylvania town in which it supposedly landed, a monument to a case UFO enthusiasts still consider unsolved.