b. January 20, 1804, in Monongahela, Pennsylvania; d. May 21, 1859, in Springfield, Illinois. Irwin lived for a short time in St. Louis, Missouri. In 1838, he joined his brother, Robert Irwin, in Springfield, Illinois. On January 31, 1844, John Irwin married Margaret Guthrie. Irwin was in business for several years as a dry goods merchant, first with his brother Robert Irwin and John Williams. Then the Irwin brothers bought out Williams’s interest. A few years later, when Robert Irwin became connected with the Marine and Fire Insurance Company, John Irwin continued in the mercantile business alone and later in partnership with Walter Davis. In 1850, Irwin was a merchant and owned real estate worth $6,000. In 1857, Irwin retired from the mercantile business due to declining health.