"I'm surprised there hasn't been a human accident before," Stotelmyer said.
One of the tablets was destroyed in 1966 when it was hit by a truck, Stotelmyer said. That tablet later was replaced by an aluminum reproduction.
There are 285 of the iron interpretive tablets in the Tri-State area, with most of them in and around Antietam National Battlefield. They measure three feet by two feet, weigh about 230 pounds and were made between 1896 and 1898.
Much of the work was done in Hagerstown and the entire project cost less than $5,000, said Richard Brown, chief of cultural resources for Antietam and Monocacy national battlefields.
Stotelmyer estimates work on the six South Mountain tablets alone could cost as much as $2,500.
A story about the making of the tablets, which appeared Oct. 17, 1896, in The Morning Herald, said, "The reading of this new history of a bloody battle on Washington County soil will become more interesting than ever."
Time, elements and other factors, however, have left their mark on the tablets. Maintenance over the years has consisted mostly of applying paint. Layers of unremoved paint had started to blur the lettering on many of the tablets.
"I guarantee you there were some of them that had the original paint on them," said Brown, who led a project to restore all of the tablets and only has about 20 left.
"It's been one of my pet projects for the past five years," he said.
The South Mountain tablets were removed in January and sandblasted to remove accumulated paint from the surface. The tablets were then painted with two coats of primer and two coats of black for the background. Finally, two coats of white paint were applied for the letters.
Local residents might be accustomed to the tablets being blue, but when they were new they had white letters on a black background, Brown said.
Selection of a site for replacement of the tablets took some work because they couldn't be moved too far from the original location, Stotelmyer said. For example, one tablet specifically describes a nearby artillery battery.
Stotelmyer said the work on the tablets is part of a larger project to make the surrounding land, which the Heritage League owns, more accessible and informative to tourists studying the Civil War.
"It's a work in progress and this is the first step," he said.