It was too large for a kestrel or a merlin. Getting closer, and the light really was as bad as above, I got some photos of it. The couple of pictures in flight are from a bit of video I took. The line on the face and the white behind the eye make it a Prairie Falcon. Only in winter and early spring do they get this far East.
It flew low across a field of corn stubble to the next row of trees by a farm.