The dramatic growth of the Lehigh Valley iron industry would not be fueled by charcoal but by anthracite coal, which would be found in large deposits in the mountains forty to eighty miles to the north. Explorers in these mountains had found outcroppings of a very hard coal that they sometimes referred to as stone coal. Small amounts of it had been used locally by blacksmiths. The industrial development of the anthracite fields had its origins in the War of 1812, when the British naval blockade of the American coastline prevented the shipment of coal from Britain or Virginia to Philadelphia. A Philadelphia Quaker entrepreneur, Josiah White, had experimented with anthracite at his nail making works. White, along with others, soon discovered that even though anthracite was difficult to ignite, it burned with a hot, clean flame–ideal for home heating and many other industrial processes. White realized that there would be a large market for anthracite if it could be economically transported from the coal deposits one hundred miles to the north. What made this project feasible was that Philadelphia lay at the confluence of the Delaware and Schuylkill Rivers both of which originated in the coal region. Unfortunately, both the Schuykill and the Delaware tributary, the Lehigh, were too shallow and rocky for navigation. To make either river a major thoroughfare an expensive set of dams, canals, and locks would need to be constructed. White became involved in a corporation established to build such a canal on the Schuykill but lost control of the project to other investors. Undaunted he decided to launch a similar enterprise on the Lehigh. His canal began operation in 1829, four years after the Schuylkill canal opened, and soon over one hundred thousand tons of anthracite annually made its way down the Lehigh and Delaware Rivers. (The Delaware canal opened in 1834).
Not content to operate coal mines and a canal, White began to contemplate the use of anthracite to smelt iron. As early as the 1820s some ironmasters had experimented with anthracite but no one had been successful. In Wales, however, ironmaster George Crane had discovered that if the blast air was preheated, he could make iron with anthracite. In 1837, White's nephew visited Crane's iron works, on other business, and learned of the new process. White and his partner Erksine Hazard convinced Crane's associate, David Thomas, to come to the Lehigh Valley and construct a hot blast anthracite furnace. He arrived in the spring of 1839 and the furnace started up successfully the following summer. Soon other Lehigh Valley entrepreneurs were building their own furnaces. By 1850, Thomas's competitors had built ten other furnaces.
The Lehigh Valley iron industry boomed in the following decades and by the early 1870s it was the center of the American industry. In 1873 Pennsylvania was the number one iron producing state with nearly half of the national output; and the Lehigh Valley was the number one region in Pennsylvania. In that year, the Lehigh Valley had 47 blast furnaces that yielded nearly 400,000 tons of iron.