If you go

The Powder Magazine will celebrate its 300th anniversary at 11 a.m. Saturday. South Carolina historian Walter Edgar will talk, and its new exhibit will be unveiled. The public is invited. For more information, contact Info@Powder Magazine.org.

Its normal hours are 10 a.m. to 4 p.m., Monday-Saturday and 1-4 p.m. Sunday.

It has withstood wars, fires, hurricanes and a great earthquake.

By the numbers

100,000

Approximate number of bricks used to build structure

3 feet

Thickest part of brick walls

$400,000

Cost of renovation in the 1990s

13 yards

Distance from a 1700s

mortar strike

(Its closest known call)

4

Number of its distinctive groin arches

(used in the design so

the building would implode

in case of an explosion)

Other lives

The Powder Magazine

also has been used as a stable, a wine cellar and a print shop.

It outlasted a plot to blow it up, a poor design and more than 250 years of functional obsolescence.

Charleston’s Powder Magazine — which marks its 300th birthday next week and is widely considered South Carolina’s oldest public building — is nothing if not a survivor.

The 900-square-foot brick and stucco hut at 79 Cumberland St. stored gunpowder for only a few decades since it was built in 1713. It has had a far longer stint as one of the city’s smallest museums.

While the building itself is very old, its exhibits are brand-new, said Alan Stello, director of the Powder Magazine and author of “Arsenal of History,” a new book on the magazine’s rich past.

“We went around the whole room and updated everything,” he said. “For the first time in its history, the story of the Powder Magazine has been properly told.”

The story begins in the early 18th century, when Charles Towne was the only walled city in English North America, and the colonists chose a spot along its northern wall to store powder.

It was built with about 100,000 bricks and designed so its roof would blow off should the gunpowder inside ever ignite — minimizing damage to nearby people and buildings.

But the magazine was considered obsolete as early as the 1740s, as the city’s walls began to come down and new homes and churches began sprouting up next door, said Nicholas Butler, public historian with the Charleston County Library.

Meanwhile, its architecture was sturdy but not effective in controlling the Lowcountry’s sticky climate.

“It’s mostly brick, but there was a wooden-frame floor and elements in other parts of it. They were experiencing pretty significant rot, and the powder was spoiling because of humidity,” Butler said.

A $400,000 renovation a decade ago found that its roof leaked, probably for centuries, and its design included timbers in the walls and foundation that rotted away long ago, compounding structural problems. It has had several roofs and several floors.

“It’s a wonderful, tough old building,” Butler said, “but as a powder magazine, it was never that successful.”

However, it was lucky.

In 1731, it managed to dodge destruction when an informant foiled a plot to blow it up as a diversion to steal from nearby homes.

In 1780, a mortar shell fell within 13 yards of the building, in what might have been its closest call. (The building was empty of powder during the Union Army’s 567-day siege at the end of the Civil War. In fact, the Manigault family used it to store thousands of bottles of Madeira wine when that war began).

Its survival also reflects the power of the press.

In 1897, The News and Courier (a forerunner of this newspaper) published a plea to save relics from the city’s colonial past.

The newly formed National Society of the Colonial Dames of America in the State of South Carolina took heed and made the Powder Magazine its first project five years later, Stello said.

That’s when they purchased it for $1,000 from the family that had owned the property for generations.

As a result, the building also plays a uniquely important role in the story of Charleston’s preservation movement: It was Charleston’s first building purchased specifically to be saved for its historical significance.

Evan Thompson, director of the Preservation Society of Charleston, said, “Looking back at the history of preservation in Charleston, it’s a landmark in that regard.”

Robert Russell, an architectural historian with the College of Charleston, said the Lowcountry has lost its earliest buildings — those built shortly after the first English colonists arrived in 1670.

“Charleston doesn’t have a lot of colonial architecture, so we tend to exalt the stuff we’ve got,” he said.

Not only does the magazine survive from the colonial era, it has not been substantially expanded or rebuilt.

There are no frills here, no heating or air conditioning, and no restrooms, public or private — just a few light bulbs.

“Its essential form is intact. It was a simple building, and it remains so,” Russell said. “It’s not hard to imagine what it looked like when it was first built.”

So in a city whose preservation hinges on finding creative new uses for old buildings, the Powder Magazine is a sort of exception — a building that has survived largely because of how well it has marked the passage of time.

Maybe more than any other downtown landmark, it reflects how the heavily militarized colonial Charleston has given way to a picturesque city considered among the world’s top vacation spots.

“It’s a beloved building,” Russell said, “not so much because it’s all that useful for stuff, but because it’s a standing reminder of the long history of the city, which is a good thing.”

Reach Robert Behre at 937-5771.