Twelfth United States Infantry.
Captain M.M. Blunt, Commanding.
At sunset, September 16, 1862, the First Battalion, Twelfth Infantry, relieved the Fourth Infantry, guarding the middle bridge over the Antietam and remained on that duty until after noon of the 17th, when it advanced in support of the horse batteries, posted on the crest of the ridge crossing the road a few feet west of this point. Winthrop's Company (G) was deployed in skirmishing order down the road and in the fields south of it to drive back the Confederate Sharpshooters, who were annoying the gunners, and continued on this duty until late in the day, when it was relieved by the Fourth Infantry, the Second and 10th Infantry and the Second Battalion of the Fourteenth Infantry.