If you think the old Winchester model 1894 your great-grandfather left you in his will is an old gun, it might be time to rethink that assessment.

Researchers in Arizona believe they have found the oldest gun ever discovered in the continental United States—a nearly 500-year-old cannon recently unearthed in the southern part of the state. According to a study published in the International Journal of Historical Archaeology, the bronze cannon, likely associated with the first European expedition through the Southwest, was discovered in 2020 on the floor of a stone and adobe building near the Santa Cruz River.

Archaeologists dated the cannon using carbon dating technology and determined it was 480 years old. It likely sat inside the ruin since 1540, when the first European settlement, San Geronimo III, was established.

Researchers report that the gun had never been fired, and they believe it was left behind when indigenous natives of the area attacked the settlement.

“The gun is an important artifact, and is no doubt the earliest known surviving firearm in the United States and one of, if not the earliest found in a reliable context in the New World,” the researchers wrote.

Wall guns like the one discovered were designed to be mounted on wooden tripods along fortification walls. Because they were lightweight and durable, such guns were perfect for long exploration expeditions.

The cast-iron weapons could fire either loads of buckshot or large lead balls. Since the one discovered in Arizona had no sights, researchers believe it was probably intended to fire buckshot.

Coronado set off on the expedition in early 1540, followed later by the main body of the expedition, which included around 2,800 people and thousands of head of livestock. According to the report, the expedition wasn’t considered successful since it didn’t find the riches and treasures the explorers sought on their journey.

The archaeological site also yielded several other prizes for researchers, including arrowheads, lead bullets and weapons parts. They believe that after the Spanish fled the attack by the Sobaipuri O’odham people in the 1540s, they didn’t return to explore the Southwest until the late 1600s.

“Europeans did not return to what became southern Arizona for another 150 years, making it the earliest and most consequential Native American uprising in the continental U.S.,” the researchers said. “This fact is surprising given that until this discovery the O’odham were thought to have played at most an insignificant role in the initial conquest episode.”