Alamo Artillery Metallurgy: Decoding 1836 Bronze Cannonballs

The earth surrounding the mission of San Antonio de Valero has held its breath for nearly two centuries. To the millions of visitors who walk its sun-baked grounds every year, the Alamo is a monument to sacrifice, a symbol of defiance, and the legendary crucible of the Texas Revolution. But to archaeologists and historians, the soil itself is a sprawling, unread book. On March 5, 2026—just one day shy of the 190th anniversary of the battle's bloody conclusion—the earth finally yielded one of its most intimately guarded secrets.

Three feet beneath the modern surface, in an undisturbed, "clean deposit" of 1836 soil, archaeologists unearthed a fully intact, four-pound solid cannonball.

To the untrained eye, a 190-year-old artillery projectile is merely a heavy sphere of corroded metal. But to historical metallurgists and military experts, this specific cannonball acts as a forensic fingerprint. It was not forged of iron, which was the standard munition for American and European armies of the era. Instead, it was cast entirely of solid bronze.

This single metallurgical distinction unlocked a wealth of historical context, painting a vivid picture of the sheer industrial, tactical, and psychological realities of the 13-day siege. The discovery has not only electrified the archaeological community but has also cast a new spotlight on the weapons, the science, and the men who fought and died under the shadow of the Alamo in 1836.

The March 2026 Discovery: A Glimpse into the Firestorm

The discovery was made during excavations tied to the Alamo Plan, a monumental $550 million preservation and expansion project aimed at protecting the historic footprint of the site. While working near the northeast corner of the historic Alamo Church, the archaeological team struck upon the artifact.

Because the soil layers in this specific deposit were perfectly stratified and undisturbed by subsequent urban development, researchers could confidently date the resting place of the cannonball to the exact time frame of the siege.

The emotional weight of the discovery was immediate. "March 5th is when we pulled it out of the ground," Dr. Tiffany Lindley, the Alamo's Director of Archaeology, explained on the site's official podcast. "I don't think words can express the feelings that we all felt." Kolby Lanham, the Alamo's Senior Researcher and Historian, recalled sprinting to the excavation unit. "That’s a literal artifact from the Battle of the Alamo," he noted, "and you’re holding it for the first time since the battle happened."

But the most striking aspect of the four-pound sphere was its composition. The bronze material immediately answered the question of who fired it.

"We can't say with 100% certainty that it came from the Mexican Army, but I would say 99% because largely the Mexican Army is using bronze cannonballs and largely the Texans are using iron cannonballs," Lanham explained. The heavy bronze sphere had waited 190 years in the dark, a silent testament to the devastating artillery bombardment ordered by Mexican President General Antonio López de Santa Anna.

The Metallurgical Divide: Why Bronze?

To understand why the Mexican Army fired bronze cannonballs at the Alamo while the Texian defenders relied on iron, one must look at the geopolitical and industrial landscapes of the 1830s.

The Iron of the Texians

Cast iron was the dominant material for artillery projectiles in the 19th-century United States and Great Britain. Iron is immensely hard, incredibly destructive against masonry, and relatively cheap to produce if a nation possesses the massive blast furnaces and industrial foundries required to smelt and cast it. The Texians—a hodgepodge army of settlers, frontiersmen, and volunteers—did not have a centralized military-industrial complex. Their munitions were a mix of captured Mexican ordnance, imported American iron, and scavenged scrap. When they fired cannons, they overwhelmingly preferred iron solid shot, though they were also known to pack their cannons with chopped horseshoes, nails, and scrap metal when proper cannonballs ran low.

The Bronze of Santa Anna’s Army

Mexico, conversely, had a vastly different industrial heritage. With a deeply rooted history in silver, copper, and tin mining, alongside centuries of Spanish colonial bell-founding traditions, the Mexican military infrastructure leaned heavily on bronze. Bronze is an alloy, primarily composed of copper and tin (and occasionally traces of zinc or lead to aid the casting process).

While an iron foundry requires staggering temperatures (over 2,100°F or 1,150°C) and massive blast infrastructure, bronze can be melted and cast at lower temperatures using smaller, more mobile foundry operations. Bronze is also highly ductile; it doesn't shatter as easily as brittle cast iron, which made it an excellent material for casting the actual cannons themselves. Consequently, the Mexican Army cast many of its solid artillery projectiles out of the same bronze alloy used for its gun barrels.

When Santa Anna’s forces marched into San Antonio de Béxar in February 1836, they dragged with them an imposing artillery train, largely cast of gleaming bronze. The four-pound cannonball unearthed in 2026 was fired from one of these Mexican field guns—likely a lighter, highly mobile 4-pounder cannon meant to break infantry lines and batter wooden fortifications.

The Arsenal of the Alamo: An Artillery Duel

The story of the Alamo is inextricably linked to artillery. In fact, the entire Texas Revolution was ignited in October 1835 over a cannon—the famous "Come and Take It" gun in Gonzales, which Mexican forces attempted to repossess. By the time Santa Anna laid siege to the Alamo in 1836, the old mission housed the largest artillery contingent west of the Mississippi River.

The Texian defenders, co-commanded by William B. Travis and James Bowie, had amassed 21 cannons of wildly varying sizes and origins. Their arsenal included:

The 18-Pounder: The crown jewel of the Alamo's defense, this massive gun anchored the southwest corner of the compound.
A 12-Pound Gunnade: A bizarre, short-barreled hybrid between a cannon and a naval carronade. How this maritime weapon ended up 150 miles inland remains one of the great historical mysteries of the Texas Revolution.
A 9-Inch Pedrero: A stone-throwing mortar used for close-quarters anti-personnel defense.
Assorted Field Pieces: Including iron 16-pounders, 8-pounders, 6-pounders, and several smaller brass and bronze 3- and 4-pounders.

Against this formidable stationary defense, Santa Anna erected aggressive siege batteries. Under the cover of darkness, Mexican artillerymen established batteries along the right bank of the San Antonio River and to the east of the mission, approximately 1,000 feet from the Alamo's walls. They unleashed a psychological and physical hellstorm.

During the first week of the siege, the Mexican artillery fired over 200 cannonballs into the Alamo compound. The bombardment was relentless, designed not just to crumble the adobe and stone walls, but to deprive the defenders of sleep and shatter their morale. In the early days of the siege, the Texians frequently engaged in artillery duels, matching the Mexican fire. Because they were starved for supplies, Texian defenders would routinely run into the plaza, pick up the fired Mexican cannonballs, and fire them right back out of their own guns.

However, by February 26, Travis realized his powder stores were depleting too rapidly. He ordered his men to stop returning artillery fire to conserve powder and shot for the inevitable infantry assault. From that point on, men like Davy Crockett relied on the precision of their long rifles, while the Mexican bronze and iron continued to rain down upon them.

Terror from the Sky: Exploding Shot and Howitzers

The four-pound solid bronze ball was not the only chilling artifact discovered by the Alamo Plan’s archaeologists. Over the past year, the team also recovered four fragmented pieces of "exploding shot" just outside the church. Interestingly, three of these fragments are bronze, and one is iron.

While a solid cannonball is a kinetic weapon—essentially a giant, hyper-velocity bowling ball designed to smash through walls and human ranks—exploding shot was the 19th-century equivalent of a modern fragmentation grenade. These hollow, spherical projectiles were typically fired from a short-barreled cannon known as a howitzer.

The Mechanics of 1830s Exploding Shot:

The Payload: The hollow bronze or iron sphere was packed tight with volatile black powder.
The Fuse: A wooden or brass fuse plug, filled with a slow-burning compound, was hammered into a hole in the shell. The artilleryman would trim the fuse to a specific length based on the estimated flight time to the target.
The Firing: When the cannon was fired, the blast from the propelling charge would ignite the fuse.
The Detonation: If perfectly timed, the shell would arc over the walls of the Alamo and explode violently in the air directly above the defenders, showering them with lethal, jagged shrapnel.

Finding these specific fragments provides physical proof of the terrifying multidimensional warfare the Texians faced. They weren't just being battered horizontally by solid four-pounders; they were being bombarded vertically by exploding howitzer shells designed to bypass their walls entirely.

The Science of Resurrection: Modern Conservation

The unearthing of these 1836 relics is only the first step; the true magic of historical metallurgy lies in preservation. When bronze and iron sit in damp soil for 190 years, they undergo severe chemical changes. Iron suffers from chloride-accelerated oxidation (rust), while bronze develops a thick, sometimes destructive patina known as "bronze disease" if chlorides are present.

The Alamo Trust relies on state-of-the-art conservation techniques, often partnering with institutions like Texas A&M University’s Conservation Research Lab (CRL), to stabilize these artifacts. In recent years, the CRL has performed miracles on the Alamo's surviving artillery pieces.

The conservation process is a meticulous science. When the lab restored the Alamo’s 6-pounder Rio Grande Cannon and a 4-pounder Spanish cannon in 2018, they placed the massive artifacts into vats of sodium hydroxide. By running an electrical current through the solution—a process known as electrolytic reduction—they successfully halted the corrosion process, essentially reversing the chemical damage. Following boiling rinses to remove residual salts, the iron was treated with tannic acid to blacken and stabilize it, sealing the cannons for future generations.

In a stunning twist during the 2018 conservation, researchers looking into the bore of the 4-pound Spanish cannon discovered an unfired cannonball still loaded inside. Jim Jobling, a research associate at the lab, noted, "While we can't say for sure, it is possible that the cannonball we found in the gun was loaded during the 1836 Battle of the Alamo, but of course, never fired."

The history of Alamo artillery preservation is also filled with bizarre, uniquely Texan anecdotes. In 2026, the Alamo proudly announced the return of an original 90-pound, three-foot-long 1836 swivel cannon. The gun had been buried by the retreating Mexican army and was discovered in 1852 by Samuel Maverick, a famed Texas land baron and Alamo survivor (having been sent out as a courier days before the fall). For decades in the 20th century, the Maverick family descendants unknowingly used the priceless 1836 combat cannon as a garden birdbath at their Sunshine Ranch. It has now been graciously donated back to the Alamo, where conservators are preparing it for display in the upcoming Visitor Center and Museum.

The Weight of History

Artillery dictated the fate of the Texas Revolution. From the opening shots at Gonzales, to the tragic massacre at Goliad—where Colonel James Fannin's hesitation to abandon his heavy cannons led to his army's capture—to the decisive victory at San Jacinto, where the famous "Twin Sisters" cannons broke the Mexican lines, ordnance was the ultimate arbiter of victory and defeat.

When the Mexican Army launched its final, overwhelming assault on the Alamo in the pre-dawn darkness of March 6, 1836, the artillery had done its job. The walls were breached, the defenders were exhausted, and within hours, the garrison was entirely wiped out. The sheer brutality of the defeat, facilitated in no small part by the bronze cannonballs and screaming howitzer shells of Santa Anna's batteries, birthed the immortal rallying cry, "Remember the Alamo!"

As the State of Texas approaches the 190th anniversary of the battle in 2026, the newly discovered four-pound bronze cannonball bridges a gap of almost two centuries. It represents the intersection of human desperation and industrial metallurgy. Carefully extracted from the earth, analyzed by modern science, and soon to be placed under museum glass, this simple bronze sphere is no longer an instrument of destruction. It has been transformed into a timeless vault of memory—a physical piece of the firestorm that forged the Republic of Texas.