This wandered into my bug tent. I captured it and later, made a specimen of it for some anatomical shots.
It looks somewhat like Agkistrocerus we have here in the guide, but I'm not at all familiar with these.
On second thought, I somehow missed a very similar fly, with an excellent series of photos by Tony Thomas, from South Carolina, Tabanus fuscopunctatus:

That looks very close, except for the lack of spots on the abdomen--see comments below.