When the Disney Company ended months of controversy in 1995 by deciding against locating its historic theme park near the National Battlefield Park in Manassas, Virginia, advocates of historic preservation had won their own battle but perhaps not their war.

Few places exemplify the problems of historic preservation as urgently as Manassas. The site of this Civil War battle, also known as Bull Run, has been encroached upon by plans for an interstate highway, a cemetery, a shopping mall, and two theme parks. As Washington continues its sprawl into the Virginia countryside, pressure...