Century-old cannonballs unearthed in San Francisco

(KRON) — A recent construction project at the Presidio Park in San Francisco turned into a cannonball run of sorts.

In August, a diverse team of experts discovered two century-old cannonballs buried at the Presidio Fire Station. The team quickly secured the area, working together to handle the rare find. KRON4 News wanted to dig deeper into the discovery, so we spoke with the Presidio Trust to uncover the story and a bit of history.

On Aug. 9th, at around 3 p.m., the Department of Public Safety was alerted about the cannonballs, referred to as an “unexploded ordnance (UXO),” said Bob Menezes, Internal Communications Manager for the Presidio Trust. The Presidio Trust Safety Officer, U.S. Park Police, and Fire Inspector arrived on the scene to establish a 300-foot safety perimeter around the area.

The Presidio Trust’s Department of Public Safety, the National Park Police, and the National Park Service teamed up with the Travis Air Force Base Explosive Ordnance Disposal (EOD) unit to assess the cannonballs. The EOD experts confirmed that the “UXO” posed no threat and provided guidance on “containment, removal, and disposal,” according to Rob Thomson, Federal Preservation Officer at the Presidio Trust.

Thomson shed light on the possible origin of the cannonballs. “These cannonballs likely date to after the Civil War when the U.S. Army began transitioning from smoothbore artillery to rifled artillery,” Thomson explained. “This shift rendered spherical cannonballs obsolete, so the Army repurposed them as decorative elements, often lining curbs and sidewalks with them. A circa 1925 photo of the Presidio Fire Station on Lincoln Boulevard (built in 1917 and still in use) shows one such ‘cannonball curb,’ a common landscape feature in the Presidio from the late 19th to early 20th centuries.”

Thomson noted there’s a good chance that the unearthed cannonballs are the same as the ones shown in the above photo, as the curb stretched through the current excavation area.

So, what other buried treasures have been found over the years? Plenty, according to Menezes. “The Presidio is a National Historic Landmark District with over two centuries of military use and many more centuries of human occupation, making it rich in archaeological resources. Trust archaeologists spend significant time protecting these deposits from construction activity by closely monitoring work crews during digging.”

As for the cannonballs, since they were confirmed as safe but were “badly corroded,” they will be discarded. Examples of similar cannonballs are currently on display at Pershing Square in the Main Post of Presidio Park, just north of the flagpole.

Want to explore even further? Materials discovered over the years during monitoring activities and archaeological research excavations can be found online here .

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