The scale of the Mercer operation would eventually be recorded by the soldiers sent to destroy it. Surviving ledgers document enslaved laborUnlike many vanished Appalachian industries whose workings are known primarily through later recollections, Mercer Saltworks left behind part of its business archive. A West Virginia historical marker erected for the site similarly describes Mercer Salt Works as supplying southwestern Virginia through the labor of both free and enslaved workers. At approximately 2 to 2:30 on the morning of Sunday, Aug. 10, the Union soldiers reached Mercer Saltworks. Whatever combination of circumstances ultimately proved decisive, the world in which Mercer Saltworks had prospered was disappearing.