He photographed many generals in the war such as, Nathaniel Banks, Don Carlos Buell, Ambrose Burnside, Benjamin Butler, George Custer, David Farragut, John Gibbon, Winfield Hancock, Samuel Heintzelman, Joseph Hooker, Oliver Howard, David Hunter, John Logan, Irvin McDowell, George McClellan, James McPherson, George Meade, David Porter, William Rosecrans, John Schofield, William Sherman, Daniel Sickles, George Stoneman, Edwin Sumner, George Thomas, Emory Upton, James Wadsworth and Lew Wallace. Brady also photographed Abraham Lincoln on many occasions.
He moved to New York City at the age of 17. By 1844, he had his own photography studio in New York, and by 1845, Brady began to exhibit his portraits of famous Americans. Brady's images were daguerreotypes.
He employed Alexander Gardner, James Gardner, Timothy O'Sullivan, William Pywell, George Barnard, and eighteen other men , each of whom were given a travelling darkroom, to go out and photograph scenes from the Civil War.
In 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, making the presentation totally new to America. No one had seen anything like this before.