Complex sentence: Fifty-four Union Army dead from the Battle of Ball's Bluff are interned in 25 graves in the half-acre plot; the identity of all of the interred except for one, James Allen of the 15th Massachusetts, are unknown.
Split into simpler sentences: Fifty-four Union Army dead from the Battle of Ball's Bluff are interned in 25 graves in the half-acre cemetery. The identity of all of the interred except for one, James Allen of the 15th Massachusetts, are unknown.