My camera is "causing" me to learn names of the various things I take pictures of. I couldn't just leave this at "tall purple flowers".
I think it is Physostegia virginiana, aka Obediant Plant. So named because it apparently will stay in position if you turn the leaves or flowers in a certain direction. Also supposedly will stay in place if it is transplanted.
It is also known as False Dragonhead ... the flower is a little like a snapdragon. Apparently there is a flower in Europe that is the "real" dragonhead.