They can be tough to pin names on, but not that tough. During the course of my time in West Virginia last week, I saw great blooming rafts of violets of all stripes, and took photos of some of them.
Two tips to greatly narrow the options if you wish to try and name an unknown violet: 1) Color. Is it white, purple, or yellow. That's easy enough. 2) is it caulescent (leafy-stemmed) or acaulescent (lacking aerial leafy stems; leaves and flowers originating from the root). If you can determine these two characters for the violet at hand, you'll have eliminated a large number of possible suspects.
Canada Violet, Viola canadensis. Our most robust species, and some plants such as the one above can resemble little shrubs. White flowers, obviously, and this is a leafy-stemmed species. The flowers are bright white with a luminescent yellow central eye, and it prefers rich wooded hillsides.
Ack! Another maddening case of Blogger absolutely refusing to post this photo right side up, no matter what I do. It should be rotated 90 degrees clockwise, and if you tilt your head that way you'll see a wonderful Northern White Violet, Viola macloskeyi, positioned properly. It much resembles the previous species, but is somewhat more robust, has green pedicels (flower stems) rather than pinkish ones, and less twisted upper petals. This species is also considerably scarcer, growing in cold saturated springy ground. I photographed this specimen at Cranberry Glades.
Should you wish to make more sense of these little plants, I will hope that this post has helped.