Probably Viola canadensis

Here is a link that might be useful: Viola

The link says that viola canadensis is purpley on the back of the bloom, and this one is all white there. Also, the petals are narrow like they look in this photo (and the canadensis seems really round).

Maybe it's simply a "gone wild" version of some cultivated violet....?

Any other native violet people out there with any other possibilities?

Thanks for looking!
Tina

Your picture does not show any detail. You might look at various websites for white Viola species.
( flower, reverse of flower, etc)

Here is a link that might be useful: Viola striata