It looks like a wild geranium. The kind you find in sunny fields.

It is hard to tell from your photo, but it looks a little like Johnson Blue.

I believe this is Hampshire purple. I grow this in my garden and when established it will create a nice big pillow of foliage and bloom. In your photo is looks to violet to be Johnson's Blue and the foliage too narrow.

WOW, Thank You. I cane looking for this exact one.! I have this growing in one of my gardens and I was told it was a Grandmas Petunia.! Then I heard it on HGTV referred to as a Geranium.! IT is beautiful and spreads lovely...!!

Kellee

Very highly dissected foliage like this is characteristic of G. sanguineum, but flower colors on this species tend more to the pinks and purples. Because of the color, I'd guess it some form of G. pratense or a pratense hybrid. And you're right, greenhouser - Geranium pratense is known as "meadow geranium" and is found growing wild in these types of locations, although it is not native to this country :-) If it self-seeds prolifically, chances are it's some sort of pratense.