This outline map of the main landmass of the United States has shading where the highest risks of nitrate contamination in ground water. Most of the shading/risk is in the mid-west area— Oklahoma, Kansas, Nebraska, edges of Iowa, eastern edge of South Dakota and boundary areas of Wisconsin. There are some areas of risk on the east and west coasts. The western areas, such as Nevada, Utah, Wyoming, Colorado, Montana, New Mexico and Arizona have no risk of contamination of ground water by nitrate.