There are also thousands of Civil War veterans buried at Green-Wood. Among them are two brothers from Maryland, Clifton and William Prentiss.
They fought on opposite sides of the war, Clifton for the Union and William for the Confederacy. Both died of injuries sustained at the Battle of Petersburg. Their nurse at Washington's Armory Square Hospital was Walt Whitman. And I didn't realize it until a few minutes ago, but he wrote about them in Specimen Days: Two Brothers, One South, One North.