How the Star Fort Got Its Shape

When it became apparent that the Confederacy was about to invade New Mexico, the garrison at Fort Union realized it had a problem. They were in the wrong kind of fort in the wrong location.

The first Fort Union had been built for warfare against Indians. It was almost unheard of for Indian warriors to attack an Army fort. Indian fighting forces generally numbered no more than a few hundred warriors. So the original Fort Union had no protective walls. And it was nestled up against a large mesa. The mesa top was an excellent location for an enemy force to pour artillery fire into the fort, but the Indians had no cannons.

All that changed with the impending invasion. The Confederates would bring with them cannons, thousands of soldiers, and a willingness to attack and beseige a well-armed enemy. So the Army built a new Fort Union.

 

Bastions and Demilunes

First, the army moved the new fort a mile away from mesa. Then, the army constructed the new fort out of a traditional, readily available fort-building material--dirt. The basic shape of the new fort was a rectangle, and it was surrounded by a ditch. The ditch was another impediment for an attacking enemy, and the dirt excavated from the ditch was used to build the fort walls.

At each corner of the rectangle, the army built a bastion. A bastion protrudes beyond the main fort wall. A defender in a bastion is able to fire at an enemy down the entire length of wall all the way to the far bastion, making it very difficult for attackers to find shelter outside the fort walls. Seen from above, the bastions look like points of a star.

For additional protection, the army added demilunes (or ravelins) to the new fort. Think of the demilune as a triangular mini-fort, with its own walls and ditch, set in front of each of the four walls of the original rectangle. Viewed from above, the four bastions and the four demilunes gave the second Fort Union the appearance of an 8-pointed star.

Star-shaped forts were a common design used in Europe beginning in the 1500s. There were a number of star-shaped, masonry forts built in the American colonies and in the early years of the country, including Castillo de San Marcos in St. Augustine, Florida, Fort McHenry in Baltimore and reconstructed Fort Ticonderoga in upstate New York.

 

Artist's rendition of the Civil War-era Fort Union.

Fort Union National Monument

Work on the second Fort Union began in the summer of 1861. Armed with picks and shovels, the new recruits to the Union Army worked day and night, 24 hours a day to build the new fort. By the following spring, the massive job was basically done. The fort covered about 33 acres. The troops had even dug a tunnel from the fort to the nearby Wolf Creek to ensure a water supply in case of a seige.

Cannons were to be mounted behind the walls of the main rectangle. The main area also had a heavily fortified "bombproof" to serve as a powder magazine, storehouses for supplies and officers' quarters. Platforms were built behind the demilune walls for soldiers armed with rifles. Barracks for the privates were also in the demilunes.

Upon completion, one officer proclaimed that it was "as fine a work of its kind as I ever saw" and "all Texas can't take it." But living conditions were less impressive. The quarters and storehouses were made of unbarked pine logs that quickly rotted and housed nesting insects. Underground rooms, including the powder magazine, were damp and unventilated. Dirt floors quickly turned to mud when it rained. Many of the troops slept in tents outside the fort, and the tunnel to Wolf Creek collapsed.

 

Aerial photograph of remains of earthen Fort Union.

Fort Union National Monument

A Precious Treasure

Earthen forts were of common construction in the Civil War years. Washington, DC, was protected by a ring of dirt forts, as were the Confederate strongholds at Petersburg, Virginia, and Vicksburg, Mississippi. There are bits and pieces of Civil War earthworks at various locations around the eastern United States, but the second Fort Union is one of the most complete, least disturbed Civil War-era earthworks in the country. The second Fort Union was added to the National Register of Historic Places in 1966.