Iron ores, like magnetite, need to be heated to remove oxygen and impurities so that the metallic iron can be made into goods.

In the Adirondacks, the source for heating iron ores was charcoal. Charcoal is made by burning wood slowly in an enclosed area - such as a pit or kiln.

Mining companies hired charcoal makers, known as “colliers,” to tend pits and kilns. In the early 1800s, most charcoal was made in pits. Colliers would stock up to 30 cords of wood in open pits. Then they tended the fires for days, making sure the flame never died out or got too big.

The iron industry used huge amounts of charcoal. From 1850 to 1880, forges and furnaces used 7,000,000 bushels of charcoal a year. Colliers needed 160,000 cords of wood to make that much charcoal, so up to 7,000 acres of forests were cut each year to feed the iron industry.