Walt Whitman in 1863, when he began his hospital visits. (LIBRARY OF CONGRESS)

George Washington Whitman, 51st New York Volunteers. (LIBRARY OF CONGRESS)

Louisa Whitman, the poet’s beloved mother. (LIBRARY OF CONGRESS)

After only a few months, the strain is etched on Whitman’s face. (LIBRARY OF CONGRESS)

Ellen O’Connor, one of Whitman’s “understanders.” (LIBRARY OF CONGRESS)

Two recent amputees among the wounded in the Wilderness. (U.S. ARMY MILITARY HISTORY INSTITUTE)

A sight in camp. The dead await burial at Fredericksburg. (USAMHI)

A hard-pressed surgeon, foreground, examines a soldier’s leg wound, Virginia 1862. (LIBRARY OF CONGRESS)

Armory Square Hospital, where Whitman spent most of his time. (USAMHI)

Interior of Armory Square, with 4th of July holiday decorations. (USAMHI)

Rare photo of a female nurse with the men. Her name was Anne Bell. (USAMHI)

Army ambulances parading down Pennsylvania Avenue in the Grand Review. (LIBRARY OF CONGRESS)

Whitman with Peter Doyle—“Pete the Great”—in 1865. (LIBRARY OF CONGRESS)