Last Friday, two Civil War-era cannonballs were found in the Presidio, officials said. The ammunition turned out not to be explosive.

Crews dug up the 10-inch-diameter cannonballs while conducting a soil remediation project adjacent to the Presidio Fire Station. With the help of Travis Air Force Base’s explosive ordnance disposal team, colloquially known as the bomb disposal squad, park officials ensured the cannonballs did not pose an explosion hazard and disposed of them safely.

Because of their hollow core and spherical shape, the cannonballs likely date from the Civil War era, says Rob Thomson, a preservationist with the Presidio Trust. After that war, the U.S. Army switched to using spherical projectiles that had greater accuracy and longer range.

In the late 19th century, the discarded round cannonballs were reused as decorative landscaping elements, lining curbs or stacked in front of home entrances, Thomson said. A 1925 photo of the Presidio fire station shows what was known as a cannonball curb, one of many scattered throughout the Presidio at the time.

During World War II, most of the decorative cannonballs were collected as war scrap, but some may have been left behind. “When these cannonball rims were pulled up and taken away, it’s not surprising that some cannonballs became dislodged and buried,” Thomson said.

Although it is “quite rare” to find such cannonballs these days, old military paraphernalia is often found on the site of the old military base, Thomson said.

“We are constantly reminded that the Presidio was a military base for over 200 years,” Thomson said. “That period of activity left behind a whole lot of things, from the buildings to the trees to the beautiful landscape to the unexploded ordnance in the ground.”

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