In the southern Arizona desert, a fragment of forgotten history has emerged from the dust: a bronze cannon, silent for nearly 500 years. This relic is officially the oldest firearm ever found in the continental United States. It was recently unearthed at the site of San Geronimo III, a doomed settlement established during the Spanish conquest in 1541.
The cannon tells a story of conquest, resistance, and one of the earliest Native American victories against European colonizers.
The Town That Vanished
In 1540, Francisco Vázquez de Coronado led 400 soldiers, their families, and about 1,500 Indigenous allies northward from Mexico. They sought the fabled “Seven Cities of Gold.” It was a grueling journey. They drove herds of livestock across mountains and deserts, relying on sparse water sources and limited supplies. By 1541, they had reached southern Arizona, where they established a settlement they called San Geronimo III, or Suya.
San Geronimo was the first European town in the American Southwest. Coronado left behind 200 to 400 people — soldiers, servants, and settlers — to build a permanent presence for the Spanish crown. So, they constructed adobe and rock buildings, tended to the sick, and defended the settlement’s perimeter with walls and firearms like the bronze cannon. But what they envisioned as a foothold for Spain was, in truth, a powder keg.
The Sobaipuri O’odham, who farmed the rivers of southeastern Arizona, were no strangers to outsiders. But the arrival of the Spanish brought abuses that ignited tensions. The conquistadors seized food, enslaved women, and punished dissent with mutilation. Noses, tongues, and hands were cut off for minor offenses. These transgressions did not go unanswered.
In the predawn hours of one fateful morning in 1541, the native Sobaipuri launched a surprise attack on the town. Accounts differ on the details, but the result was catastrophic for the Spanish. Many settlers were killed in their beds, and the survivors fled in disarray. One story tells of a priest wielding a broadsword in a desperate defense, who managed to save six Spaniards. Still, the cannon — meant to intimidate and protect — was never even loaded.
The Oldest US Gun
The bronze hackbut lay hidden for nearly five centuries, buried under the ruins of a collapsed building at the center of the battlefield.
“Not only is it the first gun ever recovered from the Coronado expedition, but consultation with experts throughout the continent and in Europe reveal that it is also the oldest firearm ever found inside the continental USA,” Seymour explained. She suspects the cannon, though obsolete by the 1540s, was likely cast in Mexico decades earlier. Early metallurgical analysis shows a lack of lead in the bronze, consistent with casting techniques used by Hernán Cortés during his conquest of the Aztec Empire.
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The cannon’s design is as fascinating as its story. It was lightweight for its time, portable enough to carry on expeditions but powerful enough to wreak havoc. From its smooth cylinder measuring 0.873 inches, it could fire a 4-ounce load of buckshot or a single, massive lead ball nearly 700 yards.
It had no sights, only a flat ledge near the touchhole where priming powder would rest. In the heat of battle, the gunner would ignite the powder with a slow-burning match cord, unleashing a thunderous blast. It was crude, loud, and terrifying — a perfect weapon for psychological warfare against adversaries who had never seen firearms before.
Its conical rear projection, the cascabel, was fitted for a wooden tiller — a pole that allowed the gunner to steady the cannon under their armpit or over their shoulder. The design was utilitarian but outdated, even by the time Coronado’s expedition brought it to the Americas.
A Non-smoking Gun
Yet the barrel, unmarked by black powder residue, tells a chilling fact: the settlers of San Geronimo never had a chance to use it. Apparently, the Sobaipuri struck before the defenders knew what hit them. The Coronado expedition had carried six hackbuts like this one, two of which are thought to have been left behind as rampart guns.
“The rampart gun was found on the floor of a collapsed mud-and-rock-walled structure that was in the center of the town and battlefield. It seems the roof of this structure was set on fire, and a wall collapsed on top of the gun, preserving it to this day. Carbon-14 dating of charcoal and luminescence dating of an unusual pottery sherd from inside the structure place this gun and the structure squarely in the Coronado time period,” Seymour and co-author William P. Mapoles wrote in a 2023 op-ed.
“This final blow seems to be the precipitating event that led to the abandonment of the wall gun, where it remained snugly encased in an eroded Spanish adobe-and-rock-walled structure [ruin] for 480 years,” Seymour and her colleagues wrote in a study published in the International Journal of Historical Archaeology, out on November 21, 2024.
A Conquest Halted
The battle at San Geronimo III was a rare moment in history: a complete rout of European forces by Native Americans. It delayed Spanish colonization in the region by more than a century. The cannon is a silent witness to that uprising, but it is not the only artifact that tells the tale.
Nearby, Seymour and her team unearthed crossbow bolts, iron arrowheads, fragments of chainmail, and pieces of broken swords and armor. These relics speak to the desperation of that morning. “It [the cannon] was left behind at or brought to San Geronimo to protect an incipient settlement,” the study notes. But the cannon’s silence became a metaphor for the failure of Spain’s ambitions in this corner of the New World.
The site itself has rewritten the map of Coronado’s journey. Historians have debated the expedition’s exact route for over a century, relying on vague journal entries and speculative terrain analysis. Now, artifacts like the cannon and early 16th-century gable-headed nails—used for horseshoes — anchor Coronado’s path with much better accuracy.
Echoes of the Past
The discovery of San Geronimo III is just the beginning. Since then, four additional campsites have been identified along Coronado’s trail, using a combination of historical detective work and modern archaeology. The evidence paints a vivid picture of the expedition: 400 soldiers and their families, supported by native allies and thousands of livestock, moving slowly through uncharted lands.
Each new find adds another layer to the story. The cannon, for instance, was cast using sand molds, a technique that left slight variations between barrels. Its exact origin remains a mystery, but researchers hope further metallurgical analysis will pinpoint whether it was made in Spain or Mexico. Preliminary results suggest the latter—which would imply that this is the oldest surviving firearm made in the New World.
Today, the cannon stands as a reminder that history, like the desert, can hide its secrets well — but not forever.