The natural resources and watershed conditions of National Park units in the New York-New Jersey area - Gateway National Recreation Area (GATE), Sagamore Hill National Historic Site (SAHI), and Fire Island National Seashore (FIIS) - are threatened by different degrees of urbanization and direct or indirect human use. Such threats as nutrient enrichment, sedimentation, exotic species invasion, water pollution, and development pose serious management concerns for these parks. Limited investigations of the status of different natural resources at or near each park have been conducted, but a comprehensive understanding of the natural resources and watershed conditions at FIIS, GATE, and SAHI is needed. This report details the sources of spatial data and metadata assembled into a Geographic Information System (GIS) for the purpose of assessing natural resources and watershed conditions at GATE, SAHI, and FIIS.