In the Northern High Plains of Texas, irrigated crop production accounts for a major portion of groundwater withdrawals from the Ogallala aquifer. The concern is that diminishing groundwater supplies will severely reduce regional crop and animal production, which in turn would impact the regional economy. The objective of this study was to develop and calibrate a groundwater model for a 4-county area (Dallam, Sherman, Hartley, and Moore counties) in the Northwest region of the Texas High Plains. This study is a major component of a comprehensive regional analysis of groundwater depletion in the Ogallala aquifer region with the purpose of understanding short- and long-term effects of existing and alternative land use scenarios on groundwater changes. A comprehensive geographic information system database was developed for this purpose. Hydrologic simulations were done using MODFLOW-2000 model. The model was calibrated satisfactorily for predevelopment time by reproducing and comparing groundwater levels for the 1950s with a correlation coefficient of 0.9. Predevelopment historical groundwater levels in the 4-county study area ranged from 955 to 1,405 m above MSL and simulated levels ranged from 930 to 1,410 m above MSL. With the calibrated model, the effect of change in land use/land cover on sustainability of the aquifer life will be studied. Our results are expected to be useful to develop and evaluate strategies to conserve groundwater in the Ogallala aquifer beneath Northern High Plains of Texas and improve regional water planning.