American textile merchant whose dry-goods store grew into a giant wholesale and retail business.

Stewart came to New York City from Ireland as an adolescent. He returned to Ireland a few years later to collect an inheritance, which he used to purchase $3,000 in Irish laces. With this stock he returned to New York and opened a small dry-goods store in 1823. His business expanded steadily until, in 1846, he built a huge marble building for his retail and wholesale operations.

Instead of haggling over prices (price) with each individual customer, Stewart set standard prices on all his goods, which was an innovation in his time. He was also systematic in his relations with his employees, paying a low wage and imposing a system of fines for failings. With the outbreak of the American Civil War, Stewart won huge government contracts to supply the Union Army and Navy with uniforms. In 1862 he built the largest retail store in the world to house his burgeoning business. He also acquired a controlling interest in many of the mills that manufactured his cloth, and he established offices and warehouses in six European countries. Stewart invested heavily in New York real estate, which added considerably to his fortune.

Stewart's charitable activities included sending a shipload of provisions to Belfast during the famine in 1847 and bringing the ship back full of immigrants, for whom he then found jobs. He also built a model town, Garden City, Long Island, with homes for working-class families.