Dr. A.R. Crook, curator of the Illinois State Museum of Natural History, analyzed the geology of Sangamon County in a 1912 pamphlet. It included the following description of the soil and rock layers underlying the county down to about 1,700 feet.
The most important economic features of Sangamon County geology, Crook wrote, were clay, sandstone and limestone deposits (used as building materials), coal, and the soil that sat atop those layers.
In 1912, 37 mines were producing coal in Sangamon County, making coal by far the county’s most valuable mineral. “No other single source of wealth contributed so much to the prosperity of the people in this county,” Crook said.
But coal still was rivaled in economic impact by the county’s farmland, he added. “Though but a foot or two in thickness, the soil is the source of millions of dollars worth of food and raiment,” Crook wrote, citing especially the Miami silt loam that covered about 17 percent of the area of the county. “No soil makes better corn land,” he wrote.
On the other hand, Crook commented, “When stuck in the mud on one of our country roads, the traveler may solace himself with the thought that there is more potential mud below him – two-thirds of all the rock for six hundred feet being ready to provide more mud as required! Our farms need never be exhausted, if we can but wash off the surface!”
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