McClellan's army reached the opposite side of the stream on the same day.
The bulk of the Confederate forces, under Longstreet and D. H. Hill, stood along the range of heights between Sharpsburg and Antietam Creek, with Longstreet on the right and Hill on the left, and Hood's division on the Hagerstown road north of Miller's farm, and near that point, in the rear, Jackson's exhausted troops were in reserve.
His lines, stretching from the Hagerstown road towards the Potomac, were protected by Stuart's cavalry. General Lee had his headquarters in a tent on a hill near Sharpsburg, where the National Cemetery now is, and from that point he overlooked much of the country that was made a battlefield the next day.
JOHN BROWN ON HIS WAY TO THE GALLOWS
Antietam Creek was spanned by four stone bridges, which were strongly guarded.
McClellan made his headquarters at the fine brick mansion of Philip Pry, about two miles east of Antietam. His army was posted in front on each side, one wing under Sumner and the other under Hooker. Farther down the stream, and not far from bridge No. 3, Burnside's corps was posted. McClellan's artillery was planted on the hills in front of Sumner and Hooker. This was the general position of the contending armies on the 16th.
This was a day of intense anxiety and unrest in the valley of the Antietam. The people, who had lived in the farm houses that dotted the golden autumn landscape in this hitherto quiet community, had now abandoned their homes and given place to the gathering thousands who were marching to the stern command of the officers. It was a day of maneuvering and getting position preparatory to the coming mighty conflict.
The two great armies now lay facing each other in a grand double line three miles in length. At one point they were so near together that the pickets could hear each other tread. It would require no prophet to foretell what would happen on the morrow.
On the night of the 16th few officers found relief from anxiety, and it goes without saying that many a soldier on this particular night, with his mind on the battle which was to be fought on the morrow, did not close his eyes in slumber.