Three-dimensional bedrock mapping of Grant County at a scale of 1:100,000 provides new baseline information on the distribution of geologic units. Grant County contains Paleozoic bedrock units ranging in age from Silurian to Cambrian. Gentle folds and small faults deform the Paleozoic sequence and were mapped based on structure contours of the base of the Platteville Formation and Prairie du Chien Group. In addition to understanding the bedrock stratigraphy and structure, this new mapping in Grant County can be used for various groundwater-related questions such as nitrate contamination, bacteria contamination, and other applied problems.