Burnside commanded the right wing, having his own,—the Ninth and First corps. General Cox commanded the Ninth after the death of Reno at South Mountain, and the appointment of Burnside to the command of the grand division.
The center was under the command of Sumner, and was composed of the Second and Twelfth corps,—his own and Mansfield's.
The left wing was commanded by Franklin, and was composed of the Fifth and Sixth corps.
General Lee's army was composed of the commands of Jackson, Longstreet, D. H. Hill, McLaw, and Walker.
An estimate of his forces in the battle of Antietam, obtained from prisoners, deserters, and spies, is ninety-seven thousand.
"It was fought for half a day with forty-five thousand men on the Confederate side, and for the remaining half with no more than an aggregate of seventy thousand,"[59] writes a Southern historian, who estimates McClellan's force at a hundred and thirty thousand.
The ground which General Lee selected for a decisive trial of the strength of the two armies is near the village of Sharpsburg, between the Antietam and Potomac Rivers. It is a quiet little village at the junction of the Hagerstown turnpike, with the pike leading from Boonsboro' to Shepardstown. Hagerstown is twelve miles distant, due north; Shepardstown, three and a half miles, a little south of west, on the Potomac.
In former years, it was a lively place. There were always country teams and market wagons rumbling through the town, but now the innkeepers have few travelers to eat their bacon and eggs. The villagers meet at nightfall at the hotel, smoke their pipes, drink a glass of the landlord's ale, and tell the story of the great battle.
The Antietam is a rapid, crooked mill-stream. It rises north of Hagerstown, on the borders of Pennsylvania, runs toward the south, and empties into the Potomac, three miles south of Sharpsburg. Its banks are steep. In some places there are limestone ledges cropping out. At low water, it is fordable in many places, but when the clouds hang low upon the mountains and give out their showers, it roars, foams, tumbles like a cataract.
Three miles northwest of the town, the Potomac makes a great bend to the east, comes within a half mile of the Hagerstown pike, then bears south toward Shepardstown.