NYS Civil Boundaries -- counties, towns, villages, etc.
NYS Streets
NYS Parcel Boundaries -- note that not all counties have publically-available parcel data
NY State Parks and Historic Sites
NYS Dams
NLCD Land Cover, New York, 2019 -- basic landcover (forests, cropland, water, developed areas, etc.)
Historical Railroads, 1826-1911 -- could assist with rail trail development
Cargill Salt Mine -- To download the data, click "Open in ArcGIS Desktop" and select the software you are using (ArcMap or ArcGIS Pro). Depending on which one you pick, the download file will be either "item.pitemx" or "item.pkinfo". These files cannot be opened from within those programs. Rather, you will need to double-click on the file, and it should automatically launch and open within the required program.