The Thomas Iron Company was a major iron-making firm in the Lehigh Valley from its organization in 1854 until its decline and eventual dismantling in the early 20th century. The firm was named in honor of its founder, David Thomas, who had emigrated to the United States in 1839 to introduce hot blast iron making in the Lehigh Valley, and now embarked on an independent ironmaking venture. The company's main and original plant was in Hokendauqua, Pennsylvania, which grew up around it; it also came to own blast furnaces and railroads elsewhere in the Lehigh Valley and mines in both Pennsylvania and New Jersey. Changes in the iron industry in the early Twentieth Century left Thomas Iron struggling to compete, and after a failed attempt at modernization and revival from 1913 to 1916, the company's assets were sold and largely dismantled during the 1920s.
David Thomas, a Welsh ironmaster, had been brought to America in 1839 to introduce the hot blast manufacture of anthracite iron by the Lehigh Crane Iron Company. Thomas projected his own company, which was organized on February 14, 1854 and chartered on April 4, 1854; it was named in his honor. Thomas left his post as superintendent at Lehigh Crane and was replaced by his son David, Jr. He became trustee of real estate, while his son Samuel was appointed superintendent.
Samuel Thomas had worked for his father at Lehigh Crane since 1843, and had also supervised the construction and blowing-in of a furnace at the Boonton Iron Works in Boonton, New Jersey in 1848. Under his direction, the new company built two furnaces on the Butz farm along the Lehigh River, establishing a community that would become Hokendauqua, Pennsylvania. Furnace No. 1 was put in blast on June 3, 1855, and Furnace No. 2 on October 27, 1855.
Some ore was supplied from local limonite deposits: in 1875, Thomas Iron owned four of these mines and held a fifth jointly with Crane Iron, leased eight and had worked another for two years. The company joined with Crane Iron, which had chartered the Catasauqua and Fogelsville Railroad in 1854, to begin construction in 1856. The rail line reduced difficult and inefficient wagon haulage to supply local ore to both companies. Thomas Iron also bought the Richard Mine near Mount Hope, New Jersey in 1856, which supplied large quantities of magnetite ore. Some magnetite was also obtained from mines at Rittenhouse Gap, at the south end of the Catasauqua and Fogelsville.