Congratulations! One of my favorites! Would love to have this framed on my wall! You should sell prints! There is a local artist who has a nationwide following, and, he paints scenes similar to this composition.
It was an amazing sky everywhere that day but especially to the east. We've had a particularly gray, cold, windy winter around here - it is nice to know such lousy weather has some plusses.
I used Photomatix Pro - you can buy it online. I just manipulated it until I got the sky looking like I remembered it - the rest went along with that. It was the sky that made me take the photo, all those boiling clouds coming from the same direction that the armies came from in 1862. But the camera would not reproduce the sky that way so I had to have the computer help.