Have you heard the story of the Horn Work in Marion Square? You know—that mysterious, unobtrusive, lumpy slab of concrete covered with oyster shells standing in the park near King Street? Did you know it’s actually a tiny remnant of a massive fortress that once controlled access to colonial-era Charleston? And it was the city’s first citadel during the American Revolution? The Horn Work is one of Charleston’s biggest secrets hiding in plain sight, and today we’ll review the most salient chapters of its must-read story.

Horn_Work_looking_northeast_2008Marion Square is Charleston’s most popular public gathering space, but few visitors recognize one of the city’s most valuable historical treasures within the park. Behind a modest iron railing located approximately 125 feet east of King Street stands a mysterious slab of gray, concrete-like material. It stands approximately six feet high, is nearly ten feet long, and just over two feet wide at its base. A small metal plaque affixed to the railing is inscribed with a few disjointed words: “Remnant of Horn Work. May 1780. Siege of Charleston.” This brief text, installed in 1883, has provided little to inspire the imagination of successive generations of tourists and locals, who often pass the familiar object without a second look.

The homely remnant preserved within that iron fence merits much more attention than it currently receives, however. The brief text on its humble plaque imparts little of the dramatic story behind the massive structure that once dominated the site of Marion Square between 1758 and 1784, and which formed one of the most impressive military posts of the American Revolution. The documentary trail of evidence that illuminates the rise and fall of Charleston’s forgotten Horn Work is fragmentary, incomplete, and scattered across the globe. It’s also a complex narrative, drawn out over a number of decades and embedded within a deep context of international political and military issues.

In short, it’s a difficult story to tell in a brief synopsis. After struggling with this topic for some years, I’m going to attempt to provide an overview of the subject today, followed by a series of more detailed segments in the near future. In my experience, one of the best ways to whittle a complex topic down to a manageable size is to create a series of questions and answers that address the most salient issues. You might have heard me describe the Horn Work in recent years as “Charleston’s tabby fortress.” All of these words, drawn from the vocabulary of eighteenth-century European military engineering and the vernacular architecture of early South Carolina, might not mean anything to readers today, so let’s begin with the basics.

What is a Horn Work?

Horn_work_illustrationIn the vocabulary of military architecture, a “horn work” is a sort of broad fortress with a central gateway situated on the outskirts of a fortified town, the main purpose of which is to defend the approach or path to the settlement from the advance of potential enemies. The name itself is derived from a characteristic feature common to all horn works: a pair of half-bastions projecting outward to the left and to the right of a central wall or “curtain” that includes a gateway straddling the pathway into town. These half-bastions, which provide defenders additional angles to fire at approaching enemies, resemble horns projecting from the sides of an animal’s head. Similarly, if such a fortification included a third bastion in the center of the curtain wall, it would be called a “crown work” because of its resemblance to a monarch’s crown.

A horn work, in the general sense of the term, is a species of military architecture described in scores of fortification textbooks published in seventeenth- and eighteenth-century Europe. It was just one of a number of different types of defensive works that all military engineers of that era were expected to understand. Every species of fortification—like a bastion, a ravelin, or a redout—served a specific function and was suited to a specific situation, and their respective designs were all dictated by a well-established set of geometric rules. In the international landscape of military fortifications, Charleston’s eighteenth-century horn work was not a unique entity. In the long history of South Carolina, however, our Horn Work (for which I’m using initial capitals) was a unique and exceptional structure that merits our attention and appreciation. If nothing else, this structure might have been the only horn work ever built of tabby.

What is Tabby?

Tabby is a type of concrete that was once commonly used in the Lowcountry of early South Carolina and elsewhere. Occasionally spelled “tappy” in historic sources, this building material transformed locally-abundant natural resources into a relatively simple and cheap alternative to traditional masonry construction. Laborers transported sand, ash, broken oyster shells, and powdered lime (derived from burnt oyster shells) to a job site or retrieved them from sources on the spot. After combining those ingredients with water to form a viscous slurry, laborers poured the tabby mixture into a temporary vertical form made of parallel wooden planks connected by wooden dowels. The dimensions of the form varied but were generally in the range of one to three feet in breadth and one to two feet in depth; the length of the form was determined by a number of variables. Once the slurry had dried sufficiently to form a solid mass, the form could be dismantled by sliding the wooden dowels out of the recently-poured slab and removing the wooden planks from each side. By reassembling the same wooden form on top of the cured tabby and repeating the process a number of times, the successive layers of tabby eventually formed a solid vertical wall of any desired height. Surviving examples of tabby work in the South Carolina Lowcountry often include dowel holes and horizontal lines that illustrate such a repeated sequence of actions.

Tabby was often used in early South Carolina to pour slab floors, to construct foundations for wooden buildings, and occasionally to form the walls of entire structures. Its use seems to have been more common around Beaufort and the Port Royal area, however, as fewer examples of historic tabby construction have been found in the vicinity of Charleston. Whatever the reason behind that fact, we know that tabby was considered a novel construction material for fortifications in the Charleston area in 1757. In February of that year, the South Carolina Commissioners of Fortifications, an administrative board created in 1736 and appointed by the governor, ordered “a trial of tabby work” for some repairs to Fort Johnson on James Island. Thomas Gordon, a local bricklayer and tabby expert, then poured a pair of parallel tabby walls to form the inner and outer faces of a broad parapet that was later filled with earth to create a solid mass. The experiment apparently convinced the commissioners that tabby was more permanent that earthen fortifications and cheaper than brickwork, and they hired Gordon to do further work at Fort Johnson and elsewhere. . . .

This story continues at the Charleston Time Machine.