In order to smelt iron three materials are required: a fuel source, iron ore and a “flux” which aids in separating metallic iron from impurities in the ore. Limestone is one of the best fluxes. The Lehigh Valley has all three; in quantity!
Just north of the Lehigh Valley, along the Lehigh River, lie immense deposits of anthracite, or hard, coal. In the late 18th century, these massive deposits were useless. Although people knew the coal would burn, no one had figured out how to produce the right conditions to maintain combustion. By 1820, speculators Erskine Hazard and Josiah White, not only had determined how to maintain a burn but had also secured the rights to some of the hardest and purest coal in Pennsylvania. They formed the Lehigh Coal and Navigation Company to mine and transport the coal to markets in Philadelphia and beyond (Halma and Oplinger 2001). Initially, however, coal was not used for iron smelting.
The Lehigh Valley contains excellent iron ore. Today, towns north and west of Allentown, such as Ironton and Orefield, contain the remains of large quarries were tons of iron ore were removed over more than 100 years. Similarly, the valley contains vast stores of limestone, which would later power the cement industry (Bartholomew and Metz 1988; Halma and Oplinger 2001).
Early in the 19th century, iron was smelted in relatively small batches in furnaces fueled by charcoal in the Lehigh Valley (e.g. at Lehigh Furnace or at Catherine Furnace at Jacobsburg). Iron made with charcoal produced a superior product, but consumed as much as one acre of woodland per day (Bartholomew and Metz 1988, 6). Iron plantations developed in remote regions on large tracts of unoccupied forest. Although foresters developed sustainable practices on these plantations in the mid-19th century, the increasing cost of the charcoal and of transporting iron to markets limited the expansion of iron production. Until coal caught on.
The combination of iron ore, limestone and coal was not enough. The three are mixed in a furnace and the burning fuel heats the ore causing melted metallic iron to sink to the bottom. However, the temperature could not be maintained high enough to keep anthracite iron burning. Recognizing this problem, Hazard and White went to Wales, to meet David Thomas, superintendent of George Crane’s iron works at Swansea. Thomas and Crane held the patent for “hot blast”- a method for pumping preheated air into the furnace to maintain a high enough temperature to ensure a consistent burn. Erskine and Hazard brought David Thomas to the Lehigh Valley in 1839 where he constructed and supervised the first anthracite coal fueled iron furnace in the valley (Barthholomew and Metz 1988).
The advent of hot-blast anthracite iron furnaces set off a virtual explosion in construction along the Lehigh River. By 1873, 55 furnaces were operating in the Lehigh Valley. Pennsylvania furnaces produced 49% of all raw iron made in the United States and the Lehigh Valley produced nearly 400,000 tons of iron, more than any other region of Pennsylvania. The dramatic increase in the production of iron made the railroads possible. By 1873 much of the iron produced in US furnaces was converted into rails in rolling mills throughout the country (Bartholomew and Metz 1988, 39-42). One of the most important was Allentown Rolling Mills.
Allentown boomed. Between 1840 and 1900, Allentown changed from a mid-size agricultural town of c. 3000 Pennsylvania Germans to a polyglot city of 35,000.
This all ended in the final decades of the 19th century. During the Panic of 1873, the insolvency of banks throughout the US brought the expansion of railroads to a halt. Iron production followed and soon, furnaces and mills were cutting back hours, paying less, laying off workers and shuttering their doors for part of the year. While the country suffered, Allentown reeled. When railroad construction resumed, new-fangled steel rails were demanded. These were produced by the Bessemer process at places like Bethlehem Iron (soon to become Bethlehem Steel). The rolling mills of Allentown did not adapt and shuttered their doors. The iron furnaces followed soon after (Hall and Hall 1987; Hellerich 1987).
Today, development of the Allentown Waterfront recognizes little of this vital history (see Figure 2). We hope that this project helps highlight not only the places and wealthy people at the center of these changes, but also the children, women and men who labored and lived in Allentown in the late 18th century.