This groundwater model archive documents a transient, regional-scale numerical model of the Long Island aquifer system that simulates hydrologic conditions for the period 1900-2019 using US Geological Survey’s groundwater modeling software MODFLOW 6 (Hughes and others, 2017). The development and calibration of the numerical model is documented in Walter and others, 2024. The model input and output files included in this data release are documented in the readme.txt. The model simulates historical water levels, stream flows, and the position of the saltwater interface in response to time-varying changes in pumping and recharge stresses for the period 1900-2019. This archive also contains input and output files for scenarios developed to simulate hydrologic conditions at annual and seasonal time scales averaged for the period 2010-2019, a five-year drought, and sea level rise of 6 feet.