Gettysburg visitors can check out a “witness” ironworks

Built in 1857 and named “Isabella,” this ironworks south of Thurmont, Maryland “witnessed” the passage of the Union’s I Corps on Monday, June 29, 1863. Part of Cunningham Falls State Park, the site is called Catoctin Furnace. At least four Maine units passed the operational furnace while en route to Gettysburg. (Brian F. Swartz Photo)

You’ve heard of a “witness tree.” For people visiting Gettysburg National Military Park, there’s also a “witness furnace,” an ironworks located down Route 15 near Thurmont, Maryland.

It’s Catoctin Furnace, preserved by Cunningham Falls State Park and easily accessible from Route 15. Perhaps all of I Corps passed the ironworks on Monday, June 29, 1863, and at least one Mainer mentioned the place in his memoirs.

Owned by the four Johnson brothers — Baker, James, Roger, and Thomas — Catoctin Furnace took shape in 1775 and “furnished 100 tons of shells used at Yorktown,” according to a Maryland highway marker. The Johnsons ran the furnace with slaves, “at least 271” in those early years, an on-site information panel indicates.

Located a short distance west of Catoctin Furnace, modern Route 15 did not exist during the Civil War, and any Union soldiers tramping north today would be bumper fodder for the vehicles tearing north on the highway. As in Maine, speed-limit signs mean little in Maryland.

Catoctin Furnace looked considerably different during the Civil War than today. Slave labor ran the ironworks until white workers were hired by the mid-19th century. (State of Maryland)

The undulating modern Route 806 preserves the actual road “up” which the 2nd Maine Battery (Capt. James Hall) and the 5th Maine Battery (Capt. Greenlief T. Stevens) rumbled on June 29. Commanded by Capt. Constantine Taylor, Co. L of the 1st Maine Cavalry Regiment protected Reynolds and his staff and provided ready-made couriers.

Past Catoctin Furnace marched the 16th Maine Infantry Regiment, commanded by Col. Charles Tilden and destined for Gettysburg immortality. Assigned to the 1st Brigade (Brig. Gen. Gabriel R. Paul), 2nd Division (Brig. Gen. John C. Robinson), I Corps (Maj, Gen. John F. Reynolds), the 16th Maine “tramped northwards” 25 miles on Thursday, June 25 to cross the Potomac River at Edwards’ Ferry and bivouac at Barnesville, Md., recalled Adjutant Abner R. Small.

Passing through the Catoctin Valley “just above Middletown” on Saturday, June 27, the Mainers reached “Frederick City, ten miles to the east” at 2 a.m., Monday, June 29, he noted.

We left there at five o’clock [a.m.], and marched [north] through Lewiston, Catoctin Furnace, and Mechanicstown [modern Thurmont]” 36 miles to reach Emmitsburg at 5:45 p.m., Small said.

A Maryland roadside marker notes a role that Catoctin Furnace played during the American Revolution. (BFS)

He offered no observation about Catoctin Furnace, which was running even as the war passed its front door.

According to Civil War Trails, “the workers of the Catoctin Furnace had little time to notice, since the charcoal furnaces were in full blast.”

Today, deciduous forests spread across the surrounding terrain, but “the landscape then looked much different,” CWT notes. “The air was filled with smoke and ash and smelled like rotten eggs … the mountainside was barren because it took an acre of trees a day to produce the charcoal needed to keep one furnace in blast.”

John Baker Kunkel owned Catoctin Iron Works. “With two furnaces in operation, production was never interrupted during the war, and the furnace workers shipped three tons of pig iron a day east to the larger arsena;s and forges that made war materials,” Civil War Trails reports.

As they did with similar iron furnaces elsewhere during their Pennsylvania invasion, passing Confederate troops would have burned everything to the ground. Kunkler was fortunate that Robert E. Lee retreated on the other side of South Mountain.

Slaves originally ran Catoctin Furnace. They lived on-site in a “three-bay stone building with three chimneys.” Set uphill from the slave quarters was the “Ironmaster’s Mansion” (only ruins today) from which the white “furnace bosses” could keep an eye on the slaves.

Sometimes a slave fled to Pennsylvania. The Mason-Dixon Line was located just above Emmitsburg, but the stream-crossed terrain challenged an escaping slave through the 1850s. White employees replaced the slaves, and Small and Hall probably saw few, if any blacks working on the grounds.

Today only a single furnace stands on this site made poignant for its African-American cemetery, reached by a well-marked trail. Constructed “of local field stone” in 1857, the furnace was called “Isabella,” and its massive chimney (also called a “bosh”) was lined with fire bricks.

Converted to coal in 1873, Catoctin Furnace ran until February 1903. Maryland maintains the site, located about three miles south of Thurmont.

Source: Harold Adams Small, ed., The Road to Richmond: The Civil War Letters of Major Abner R. Small of the 16th Maine Volunteers, Fordham University Press, New York, 2000, pp. 96-97

“Swartz delves into the personal stories of sacrifice and loss…” — Civil War News

If you enjoy reading the adventures of Mainers caught up in the Civil War, be sure to like Maine at War on Facebook and get a copy of the new Maine at War Volume 1: Bladensburg to Sharpsburg, available online at Amazon and all major book retailers, including Books-A-Million and Barnes & Noble. —————————————————————————————————————–

Available now: Passing Through the Fire: Joshua Lawrence Chamberlain and the Civil War, released by Savas Beatie.

This new book chronicles the swift transition of Joshua L. Chamberlain from college professor and family man to regimental and brigade commander and follows him into combat at Shepherdstown, Fredericksburg, Gettysburg, and the Petersburg and Appomattox campaigns.

Drawing on Chamberlain’s extensive memoirs and writings and multiple period sources, historian Brian F. Swartz follows Chamberlain across Maryland, Pennsylvania, and Virginia while examining the determined warrior who let nothing prevent him from helping save the United States.

Order your autographed copy by contacting me at

Passing Through the Fire is also available at or


Brian Swartz can be reached at He enjoys hearing from Civil War buffs interested in Maine’s involvement in the war.

Brian Swartz

About Brian Swartz

Welcome to "Maine at War," the blog about the roles played by Maine and her sons and daughters in the Civil War. I am a Civil War buff and a newspaper editor recently retired from the Bangor Daily News. Maine sent hero upon hero — soldiers, nurses, sailors, chaplains, physicians — south to preserve their country in the 1860s. “Maine at War” introduces these heroes and heroines, who, for the most part, upheld the state's honor during that terrible conflict. We tour the battlefields where they fought, and we learn about the Civil War by focusing on Maine’s involvement with it. Be prepared: As I discover to this very day, the facts taught in American classrooms don’t always jibe with Civil War reality. I can be reached at