This 850-Foot Natural Limestone Tunnel Became a Secret Confederate Gunpowder Factory During the Civil War

Natural Tunnel State Park, Virginia

Deep in Virginia’s hills sits a tunnel carved by water over millions of years. During the Civil War, Confederate soldiers turned its caves into a secret saltpeter mine, scraping bat guano from cave walls to make gunpowder.

Here’s how it became a wartime factory.

Natural Tunnel State Park

Stock Creek carved this massive limestone passage through Purchase Ridge over thousands of years. More than 850 feet long and reaching the height of a 10-story building, Natural Tunnel ranks among Virginia’s most impressive geological features.

Confederate authorities recognized the strategic value of this area during the Civil War. They mined nearby limestone deposits for saltpeter, a crucial ingredient in gunpowder production.

The railroad tracks now running through the tunnel came much later. The South Atlantic & Ohio Railroad completed this route in 1890, decades after the Civil War ended.

Southwest Virginia’s Strategic Importance

Virginia contributed more mineral resources to the Confederate war effort than any other Southern state. The southwestern quarter held deposits of saltpeter, lead, salt, iron, and coal vital for military operations.

Saltpeter from Virginia caves supplied nearly 30 percent of the Confederacy’s domestic gunpowder needs. This critical shortage forced Richmond to establish the Niter and Mining Bureau in 1863.

Union commanders understood that cutting off these supplies would cripple Confederate armies. Federal cavalry repeatedly targeted mining operations throughout the war.

Confederate Saltpeter Operations

Limestone caves provided ideal conditions for naturally occurring saltpeter. Calcium nitrate leached from bat guano and soil mixed with potash created potassium nitrate—the key ingredient in black powder.

Confederate soldiers mined these deposits from caves across Virginia. The areas surrounding Natural Tunnel yielded valuable saltpeter from smaller caves and limestone outcroppings.

Mining crews worked with basic tools, scraping cave soil into wooden hoppers. Water poured through the soil dissolved the nitrates, which workers then processed into usable saltpeter crystals.

The 64th Virginia Mounted Infantry

Men from Scott County and surrounding areas formed the 64th Virginia Mounted Infantry in December 1862. This regiment recruited heavily from mountain communities near Natural Tunnel.

The unit fought as infantry but moved on horseback, allowing rapid deployment across the rough mountain terrain. The 64th primarily defended southwestern Virginia’s vital resources and communication lines.

Local knowledge gave these troops significant advantages. Many soldiers grew up hunting and farming in these mountains and knew every trail, cave, and crossing.

Union Cavalry Presence in East Tennessee

Federal forces secured control of East Tennessee by late 1863. Union commanders established bases for cavalry operations against Confederate targets in Virginia. The 2nd Ohio Cavalry and other mounted units patrolled the border region.

These experienced horsemen specialized in rapid strikes into Confederate territory. Union cavalry targeted Confederate supply lines, communications, and resource operations. Their raids aimed to destroy infrastructure rather than hold territory.

Planning the Raid

Union intelligence officers identified active saltpeter mining near Natural Tunnel in March 1864. Colonel Augustus Root, who had previously destroyed similar operations, planned the response.

Root selected experienced cavalrymen from regiments stationed in East Tennessee. His force numbered approximately 200 mounted troops armed with carbines and revolvers. The mission called for a swift cross-border raid to capture or destroy mining equipment, wagons, and processed saltpeter.

Cavalry units traveled light for speed, carrying minimal supplies.

Confederate Defense Preparations

Confederate scouts noted unusual Union cavalry activity near the Tennessee border. This intelligence reached the small guard force at the Natural Tunnel mining operations. The defense detachment consisted of twenty cavalrymen from the 64th Virginia and local Home Guard volunteers.

These part-time soldiers assembled quickly when warnings came. Mining supervisors ordered workers to prepare all equipment and processed saltpeter for immediate evacuation. Guards established observation posts on ridges overlooking likely approach routes.

The Union Advance

Federal cavalry crossed into Virginia after midnight. Their column followed creek beds and wooded valleys to mask their movements from Confederate lookouts. Local Union sympathizers guided the troops through mountain passes.

These civilian scouts knew which farm families supported the Federal cause and would not sound alarms. The cavalry force avoided main roads and settlements. They rode in single file through narrow passages to reach Stock Creek valley.

First Contact and Confederate Retreat

Confederate pickets spotted Union cavalry approaching at first light. Their warning shots alerted the mining camp, giving workers precious minutes to escape. The small Confederate force faced overwhelming numbers.

After a brief exchange of gunfire, they pulled back toward Natural Tunnel, covering the miners’ retreat. Workers hastily loaded wagons with processed saltpeter and essential equipment. They abandoned heavier items that could not be moved quickly.

The Chase Through Stock Creek Valley

Union cavalry pursued the retreating Confederates along Stock Creek. The limestone gorge narrowed as they approached Natural Tunnel, restricting movement to the creek bed. Rock outcroppings and fallen trees created natural obstacles.

Confederate riders knew where to cross the creek and which banks provided stable footing for horses. The Union pursuit split into smaller groups as the terrain forced them to navigate different passages. This diminished their numerical advantage.

Battle at Natural Tunnel

Confederate defenders took positions among the massive rock formations near Natural Tunnel’s entrance. The limestone walls provided natural cover against Union fire. Federal troops dismounted to advance on foot through the difficult terrain.

Horses would have been too vulnerable in the narrow confines of the gorge. Sharp firing continued for thirty minutes as Union soldiers attempted to flush out the defenders. The narrow approaches limited their ability to bring superior numbers to bear.

Visiting Natural Tunnel State Park

Natural Tunnel State Park welcomes visitors at 1420 Natural Tunnel Parkway in Duffield, Virginia. The park preserves both natural wonders and historical sites. A chairlift carries visitors to the tunnel floor where trains still pass through daily.

The park features camping facilities, hiking trails, and educational programs about the area’s natural and cultural history.

Read More from wheninyourstate.com

• 6 Marines Raised a Flag on Iwo Jima — Only 3 Saw the Arlington Memorial They Inspired
• This Virginia Tobacco Farm Produced America’s Most Influential Black Educator From a One-Room Slave Cabin
• Thomas Jefferson Spent 40+ Years Building This Mountaintop Mansion That’s Now on Every Nickel