John Roach & Sons was a major 19th-century American shipbuilding and manufacturing firm founded in 1864 by Irish-American immigrant John Roach. Between 1871 and 1885, the company was the largest shipbuilding firm in the United States, building more iron ships than its next two major competitors combined. It was also by far the largest contractor to the U.S. Navy during this period, and at its peak is said to have been the nation's largest employer behind the railroads.