Trifolium pratense L., red clover, the only red species; other six listed for this area are white-pinkish.
Ain't the leaf edge way too serrated to be T. pratense? I haven't come across such a plant yet, at least.
Ditto to Axel on not T. pratense; the flowers (individually on the flowerheads) are pendulous, which isn't a T. pratense character.
OK, found one more that might fit: Trifolium kingii ssp. macilentum, syn. Trifolium macilentum. I photographed it myself, but forgot. Ageing... http://www.flickr.com/photos/zharkikh/8810798426