During the fall of 1945, as part of the program for the development of the resources of the Missouri River basin, the United States Geological Survey began a new series of groundwater investigation in Nebraska. Those studies were coordinated with the already existing program of ground-water studies that was begun in 1930 by the U.S. Geological Survey in cooperation with the Conservation and Survey Division of the University of Nebraska. Most of the water-level measurements in this report were obtained and compiled as part of the Missouri Basin Development Program.