The splendid water supply of Champaign County is accounted for by the presence of the glacial drift, which forms the striking feature of the surface geology of Champaign County. Miss DeEtte Rolfe, who has written much and well on this subject, explains the matter thus: “Irregularly interspersed in this drift are long strips and beds of gravel which have their outcrops on the flanks of the moraines. These, being surrounded by the dense clay, form pockets which become reservoirs for the storage of water. It is on these reservoirs that the county must rely for its water supply. The water obtained from them is of good quality, except in the somewhat rare instances where the outcrop of the gravel bed is so situated as to be exposed to contaminating influences, or in those cases, which should never occur, where the wells themselves are contaminated. As these gravel beds are distributed through the drift at different depths, the well, even on adjoining lots, may vary in depth. The quantity of water furnished by a well is governed by the size of the gravel bed from which it draws its supply. The deep wells of the county generally draw from the beds deposited between the two sheets of drift; their difference in depth depends on the irregularities of the first drift surface.” What is termed the “Artesian Water Region of Illinois” extends a short distance into the northeastern portion of Champaign County. It is simply a stratum of water-bearing sandstone, overlaid by a thick stratum of tough clay, which confines the water to the sandstone level. Wherever holes are drilled through this overlying clay, the confined waters of the sandstone rise to the surface through the outlets, furnishing an economical and valuable supply of water for agricultural purposes. This stratum of sandstone is called the St. Peter’s, and is supposed to be the same stratum that supplies artesian water to the counties of LaSalle, Grundy, Will and Cook.

Source: A Standard History of Champaign County, Illinois, by J. R. Stewart, published by The Lewis Publishing Company, Chicago And New York, 1918.