This digital geospatial data set contains the locations, values, and uncertainties of hydraulic-head observations used in the calibration of the transient model of the Death Valley regional ground-water flow system (DVRFS). The hydraulic-head observations were developed by compositing one or more water-levels measured in wells throughout the DVRFS model ___domain, a 45,000 square-kilometer region of southern Nevada and California. To develop hydraulic-head observations, nearly all available water levels for the DVRFS region through 2004 were compiled in Ground-Water Site Inventory (GWSI), the ground-water component of the U.S. Geological Survey (USGS) National Water Information System (NWIS) database. Water levels suitable for developing hydraulic-head observations representative of regional, steady-state (pre-pumping) and transient (affected by pumping) ground-water flow conditions were identified through analyses. The resulting water levels were averaged by year and for each well to produce 4,899 hydraulic-head observation values at 868 wells. The uncertainty of each hydraulic-head observation was statistically quantified from the values of uncertainties associated with well altitude and ___location, nonsimulated transient stress, measurement accuracy, model discretization, and pumpage estimates.