Mapping & GIS Resources
Just a handful of the available resources - mostly free and open source, or offering a free version.
If you have anything to add please leave a comment!
Open Aerial Map
MD State Data Center
Open Street Map
MD DNR GeoSpatial Data Center
NOAA GLOBE Ditigal Elevation Model
The North American Transportation Atlas
US Governmental Maps at GeoData.gov
US Census data portal
WONDER portal for CDC health statistics
Stanford Medical GIS data sources