Born in Boston, Massachusetts, Homer started an apprenticeship to the Boston commercial lithographer at the age of 19. By 1857 he had started an independent career, employed as a free-lance illustrator for such magazines as Ballou's Pictorial and Harper's Weekly.
In 1859 he opened his own studio in New York City, where began his career as a painter.
Harper's sent Homer to the front during the American Civil War, where he did sketches of battle scenes and mundane camp life. Although these did not gain him much note at the time, they were to influence much of his later work.
Back at his studio after the war, Homer set to work on several war-related paintings, among them Sharpshooter on Picket Duty and Prisoners from the Front. After exhibiting at the National Academy of Design, Homer traveled to France in 1867 and began practicing painting landscapes while continuing to work for \Harper's. He began to paint in watercolor, and in 1875 he ended his career as a commercial illustrator, concentrating on his painting.
Homer began to gain acclaim as a painter in the late 1870s and early 1880s. His 1872 composition, Snap the Whip, was shown at the 1876 Centennial Exposition in Philadelphia, Pennsylvania.
He travelled widely and spent two years (1882-83) in England, where his boyhood interest in the sea was rekindled. He moved to Prout's Neck, Maine (near Scarboro) and began painting seascapes, for which he is perhaps best known. Notable among these are Banks Fisherman, Eight Bells, Gulf Stream, Rum Cay, Mending the Nets, and Searchlight, harbor Entrance, Santiago de Cuba. In order to find locations for his seascapes, Homer often took trips to such locations as Florida and the Caribbean.
Homer died at the age of 74 in his Prout's Neck studio. His painting, Shoot the Rapids, remained unfinished. Homer's works, already in great demand during his lifetime, are widely sought today.