Visitors to the West Woods who venture over to the 15th Massachusetts Monument often are surprised to find traffic zooming by not 25 yards away. This is Route 65 which connects Hagerstown and I-70 with Sharpsburg.
If you stood on the same spot on September 10, 1862 you would notice the land gradually falling away to the Alfred Poffenberger farmstead of a cabin, barn, orchard, haystacks and corn (see earlier posts). You would also see a wooden road that if you took it north would come upon the Nicodemus farmstead. If you stood on the spot seven days later, you would be in the middle of the fierce firefight between Gorman's brigade of Sedgwick's Division and remnants of Jackson's Division who were occupying the farmstead. If you stand there today, you would look over a high speed highway that has obliterated all remains of the farm lane and much of the topography of this part of the battlefield.
The "old wood road" of 1862 eventually became a paved country road and a century later was widened to the present Route 65. The first illustration (left) in this post shows the widening of the road around 1962. The exact location of this construction is difficult to pinpoint but there seems to be a parallel road to the east visible through the woodline which could only be the Hagerstown Pike. The high ground rising to the right (or east) of the Pike resembles the high ground around the Miller Farm and, if so, the location of this photo would be north of the Alfred Poffenberger farmstead.
As Route 65 approaches the park from the north it skirts west of the old Hagerstown Pike at the Joseph Poffenberger farm and then rejoins the Pike south of the Visitor's Center. Up until the last decade, the highway lay west of the Park's boundaries. Now, with the acquisition and donation of land to the Park, it runs through the National Park Service controlled property.
Regardless of who controls the land west or east of the highway it constitutes a high-speed bypass dividing the opposing lines of Gorman's Brigade (Sedgwick's Division) and the remnants of Jackson's Division in a "field of grain, hay-stacks, buildings, and a thick orchard."[2a]
Carmen narrates: "The [15th] Massachusetts regiment...came directly in front of the Alfred Poffenberger buildings...As it gained the summit of a slight elevation, its left became hotly engaged with Jackson's Division...many of them covered by the barn, stacks, and rock ledges, not over twenty-five yards beyond the wood road bordering the west edge of the woods." 
The second illustration is a detail from the Hotchkiss map showing the Alfred Poffenberger farmstead. I have added arrows and numbers to help orient the following two photographs.
The next illustration is a view, taken from the 15th Massachusetts monument [Hotchkiss map reference 2], that shows Route 65 as it heads into Sharpsburg.
To the right of this photo is the Alfred Poffenberger Farmstead (obscured by trees) and to the left is the western edge of the West Woods.
Note the location of the original Army interpretive markers that mark the west and east boundaries of the original automobile tour that ran through this part of the park.
The last photo looks north [Hotchkiss reference 1] and shows more clearly the original Army auto tour route.
Remnants of the original curbing are visible just to the left of the retaining wall. The 15th Massachusetts Monument is just to the right of this photo.
Someday, a wealthy benefactor may donate money to the Park to make Route 65 an underground bypass much like those in Colonial Williamsburg and Yorktown.
Until then visitors will enjoy the Harleys, Winnebagos, and F-150s that make their way along this historic site.
 Carmen, p. 263.
 Park Ranger Alann Schmidt kindly furnished photos of the widening of Route 65.
[2a] Lt. Col. John W. Kimball, 15th Mass., September 20, 1862. Official Reports, Series 1, Vol XIX, Part 1; retrieved from Antietam on the Web, July 31, 2009.
 Carmen, p. 261.