Born in Keeseville, New York, on April 4, 1843, William Henry Jackson was a self-taught artist who, at the age of 15, began working as a retoucher in a photographer's studio. He was successful in this pursuit and later moved to a more prosperous studio in Rutland, Vermont. He honed his artist's skills with the retouching work, but also learned a great deal about the young art of photography, a skill that would stand him in good stead later in life.
In 1862, with the onset of the Civil War, Jackson enlisted in the Union Army. His unit spent most of its time on garrison duty. Though present at the battle of Gettysburg, he was stationed in the rear areas guarding supply trains and saw no action. Mustered out in 1863, he returned to Vermont where he went to work in Style's Photographic Gallery in Burlington.