Most of these maps are derived from 1:24,000-scale maps, they show distances and contour intervals in meters. Contours are at intervals of 5, 10, 20, or 50 meters, depending on terrain relief. Some 1:100,000-scale quadrangle maps are published as planimetric editions, meaning no contour lines are present. Less detail is shown on these county maps because of space restrictions at the smaller scale, for more detail you may want to look at the 7.5 Minute quadrangle maps.
Limited quantities and quadrangles available.
PRAIRIE RESEARCH INSTITUTE
607 E. Peabody Drive, MC-700
Champaign, IL 61820