Eighty Years' Progress of the United States: from Revolutionary war to the Great Rebellion, p. 176 (1864)

Charcoal Roads
Thomas Prentice Kettell

In marshy forests charcoal roads are made. Timber from 6 to 18 inches thick is cut, 24 feet long, and piled up lengthwise in the centre of the road in such a manner that the pile will be about 12 feet high. This is covered with earth, taken from ditches on either side. When the wood is charred, the coal is raked down to the width of 10 feet, with a depth of two feet in the centre and one at the aide. Such a road becomes very compact, and free from dust. Such a one in Michigan cost $660 per mile.