Geranium pratense /Geranium Family
This is a common yard weed (along with the dandelions, chickweed, blue field madder, corn salad, and speedwell in this picture!). It has interesting beak-shaped seed pods which throw their seeds when they ripen and split. I found this one blooming in Oak Ridge in late April. Close-up of flower follows.
Where seen: Great Smoky Mountains NP, Warriors' Path SP, Widespread