I have a large number of shapefiles (>500) representing species' ranges for North America. I am wondering how I could open them all automatically, without having to open them one at a time in ArcGIS? The shapefiles are nested in a folder for each species, and then in a folder for groups of species by family.
If all of the data is the same type like polygon, you can try to use arctoolbox to merge them.
ArcToolbox -> Data Management toolbox -> General toolset -> Merge
There are two method to do merge all of your data including python and arctoolbox.