Where slept Mansfield on the night of September 15th, 1862?

I recently spent a really fun afternoon in the West Woods at Antietam with Nick Picerno and Tom Clemens at the request of Larry Freiheit, who is writing a biography of General Joseph King Fenno Mansfield. Larry isn't sure that I got it right in my book when I included the above image and stated that Mansfield spent night of September 15th at Nicodemus Mills, a few miles east of Keedysville. (The also book has a really cool letter in it about there night at the location.)

Recently I had a chance to get back to reading Tom's latest volume of Carman's Maryland Campaign, and it mentions the slumber in question, so I thought I would quickly jot the notes down here, for the benefit of my memory as much as for Larry.

On page 24 of Carman/Clemens (hereafter CC) it reads, "During the afternoon and night of the 15th McClellan's forces moved to the positions assigned to them...Mansfield's (Twelfth) Corps was at Nicodemus Mills or Springvale." Here is the great clue. There are a few Nicodemus houses on the old maps up near the town of Boonsboro. And the Twelfth Corps did come down off of Turner's Gap. But I imagine Mansfield probably turned down what is now Rt. 67 to the Old Sharpsburg Road in order to relieve congestion. But it is Springvale that dials us in.

If you Google Springvale (http://lmgtfy.com/?q=springvale+md+map)...Voila! Case closed. I was nervous there for a minute.

Postscript: On page 24 of CC, talking about the morning of September 16th, it reads, "During the forenoon the Twelfth Corps advanced from its bivouac near Nicodemus' Mill and massed in a field west of Keedysville..."

Thoughts...? If anyone knows of his movements here, I would love to hear about it. I think Alpheus Williams probably wrote about this march.