Mathew B. Brady was born to Irish immigrants Andrew and Julia Brady about 1822 in Warren County, NY. He left home at about age 17 to study with the artist William Page in Saratoga Springs, NY, in 1839. Shortly thereafter, both men moved to New York City where Page introduced Brady to Samuel Morse who had just returned from France where he had learned about the new art of photography from the inventor, Daguerre.
By 1844 Brady had opened his own photography studio in New York City and begun his career. With his energy, youth and enthusiasm, he set about to photograph all the famous people he could (and the list is impressive). In 1848 he opened a studio in Washington, DC, and, according to Wikipedia, met and later married Juliette Handy. In 1851 he entered a collection of 48 portraits in the Crystal Palace Exhibition in London and won one of 3 prizes for photography; the other 2 prizes also went to Americans. In 1858, he opened a permanent gallery. When the Civil War broke out, he took his photographic equipment to the First Battle of Bull Run where he very nearly was captured. Perhaps because of his failing eyesight, he opted to hire other photographers to document future battles while he remained at the studio in Washington. He outfitted a score of photographers with traveling darkrooms and supervised them; in the practice of the day, all photos taken were attributed to him. After the Battle of Antietam, he presented an exhibition in New York entitled , "The Dead of Antietam". For the first time, the awful realities of war were brought home to people who were not close to the action.
Brady spent over $100,000 in the Civil War venture, hoping that the government and historical societies would buy the photos afterwards but, by then, most people were so tired of the war and the toll it took that no one was interested. Brady was forced to sell his New York studio and go into bankruptcy. Congress granted Brady only $25,000 in 1875. Depressed and penniless, he became an alcoholic and died after a streetcar accident in New York City in January 1896. Veterans of the 7th New York Infantry provided a decent burial for him in the Congressional Cemetery in Washington, DC.
The 1870 census of Washington, DC, Second Ward, shows M. B. Brady, age 40 and an "artist" boarding at the home of Marcia A. Buckly. No wife is with him, but there is another artist, E. L. Townsend, among the other boarders. Because he traveled so much, it is difficult to find him in other censuses. His father appears in the 1830 census of New York (Mathew is one of the two males age 5-10 years). The complete Mathew B Brady Collection of Civil War Photographs is available on Footnote. You can search by the name of the person or event, or browse them in the order in which they were cataloged.
Mathew B. Brady was, of course, not the only photographer busy during the Civil War. Also of note was Charles L. Lochman of Carlisle, PA, who was also born about 1822. Lochman had his studio at various locations in Carlisle (at Marion Hall from Nov 1862-Jan 1865, and on East High Street in 1872). His studio at 21 West Main was taken over by J. N. Choate in 1875. Lochman appears in the 1850 census of Allentown as a "Daguer artist", the 1860 census of Carlisle as an "artist", and the 1870 census of Carlise as a "Daguerotypist". Although not as well known as Brady, he was responsible for the documentation of the devastation of Chambersburg, PA, by the Confederate army in 1864. You can see his photos and read the description at the link below.