In January, park officials participated in a visibility test, and the tower would be visible in about 70 percent of the park, Howard said. The officials were asked to provide feedback to a consultant, and Howard said he wrote that the tower would be a "major intrusion into the battlefield viewshed."
"Any modern intrusion on it really detracts," Howard said.
The "stealth telecommunications structure" would look like a silo tower, said Michael Hofe, president of Liberty Towers, which is exploring the possibility of erecting such a structure in the greater Sharpsburg area.
Hofe, a Washington County native, said visitors to the battlefield might be able to see about 30 feet of the 120-foot tower above the tree line.
"They would see the top of a farm silo," Hofe said.
The Civil War Preservation Trust publishes its list of endangered battlefields annually.
"One of the most effective tools in our arsenal is public awareness," said Jim Campi, a spokesman for the organization.
The tower would "cast quite a shadow on other parts of the battlefield," he said.
Campi called the possible tower the "most egregious" cellular tower proposal the CWPT has encountered.
The tower would be in a location that is zoned appropriately, Hofe said. Several communications companies are interested in the tower, he said.
Two traditional cellular towers already are visible from the battlefield -- one between Sharpsburg and Keedysville and the other south of Boonsboro, Hofe said.
Three other sites in the Tri-State area were named to a list of 15 "at-risk" battlefields. Those sites are South Mountain State Battlefield, Hoke's Run in the area of Falling Waters, W.Va., and a battlefield in Shepherdstown, W.Va.