I'm specifically looking for one that lets me display a map of US states with each one as it's own "object" in the sense that I can control the color, on click, and on mouseover of each one individually.  GTK is my personal preference, but at this point I'd settle for just about anything.  The application itself will be written in Python, FWIW.
If you consider Qt, consider also throwing in kdelibs dependency, 
  then you'll have marble widget, which handles maps in neat way.

Thanks for advertizing Marble. But you are incorrect: 
The Marble Widget doesn't depend on kdelibs at all. It just depends on Qt (>=4.3).
Additionally Marble also has just received Python bindings.
I think that the given problem can be solved using Marble. Would just take a few days of work at max. If you have questions about Marble, feel free to ask us on our mailing list or IRC.
Does anyone know of a widget for a desktop toolkit(GTK, Qt, WX) for displaying a map of US states?