Brady's efforts to document the Civil War on a grand scale by bringing his photographic studio right onto the battlefields earned Brady his place in history. Despite the obvious dangers, financial risk, and discouragement of his friends, Brady is later quoted as saying "I had to go. A spirit in my feet said 'Go,' and I went." His first popular photographs of the conflict were at the First Battle of Bull Run, in which he got so close to the action that he only just avoided being captured.
He employed Alexander Gardner, James Gardner, Timothy H. O'Sullivan, William Pywell, George N. Barnard, Thomas C. Roche, and seventeen other men, each of whom was given a traveling darkroom, to go out and photograph scenes from the Civil War. Brady generally stayed in Washington, D.C., organizing his assistants and rarely visited battlefields personally. This may have been due, at least in part, to the fact that Brady's eyesight had begun to deteriorate in the 1850s.
In October 1862, Brady presented an exhibition of photographs from the Battle of Antietam in his New York gallery entitled, "The Dead of Antietam." Many of the images in this presentation were graphic photographs of corpses, a presentation totally new to America. This was the first time that many Americans saw the realities of war in photographs as distinct from previous "artists' impressions".
Following the conflict, a war-weary public lost interest in seeing photos of the war, and Brady’s popularity and practice declined drastically.