A MODFLOW-2005 model, using the SWI2 package, was developed for the Sandy Hook Unit, Gateway National Recreation Area (hereafter Sandy Hook) in New Jersey to evaluate the response of groundwater resources to expected sea-level rise (SLR) and changes in groundwater recharge associated with global climate change. The National Park Service (NPS), among other agencies, is mandated to evaluate the effects of global climate change on NPS parks and promote resiliency and sustainability of park resources to the extent possible. Sandy Hook is visited by thousands of people each year who take advantage of the historical and natural resources and recreational opportunities which are threatened by global climate change, including SLR, changes in precipitation and groundwater recharge, and changes in the frequency and severity of coastal storms. Fresh groundwater resources are important to the ecosystems of Sandy Hook. The Bayside Holly Forest, one of only two known old-growth American holly (Ilex opaca) maritime forests, is particularly vulnerable to global climate change because of the proximity of the water table to land surface in low-lying areas and the potential for saltwater intrusion and inundation. Groundwater-flow simulations completed for this study include a Baseline scenario, three SLR scenarios (0.2, 0.4, and 0.6 meters [m]), two Recharge scenarios (a 10-percent Increased Recharge scenario and a 10-percent Decreased Recharge scenario) and a scenario with 0.6 m of SLR and 10-percent increase in recharge. Understanding the possible effects of SLR and changes in recharge will allow the NPS to allocate scarce resources to best prepare for and manage climate-change-driven changes in the groundwater system and the subsequent effects on park ecosystems. This USGS data release contains all of the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20205080).