Workers employed or owned by Thomas Johnson, a lawyer who later became the first governor of Maryland, and his brothers Roger, Baker, and James built Catoctin Furnace, with the Johnsons overseeing construction beginning in 1775 and the furnace in blast in time to provide ammunition to General George Washington and his army. At least 271 enslaved people of African ancestry made up the bulk of Catoctin Furnace's earliest workers, and the furnace depended heavily on the labor of enslaved and freed African Americans until the middle of the nineteenth century, when their labor was replaced by that of European immigrants. Catoctin Furnace village later included multiple furnaces, including Deborah, completed in 1873 as the final of the three, or possibly four, furnaces built at Catoctin, and the site also included features such as the Isabella stack, a casting shed, slave quarters later converted to a mule barn and then a blacksmith shop, and Monocacy Valley Railroad tracks.