12th United States Infantry, First Battalion

"...Camp at Tenallytown was broken on the 9th [of September, 1862], and the battalions, commanded respectively by Captains Blunt and Anderson, advanced through Rockville to Frederick, thence to Middletown, where bivouac was made on the 14th. Crossed South Mountain, 15th, to Porterstown, forming part of the advance. There was some harmless artillery fire in the evening.

During the first part of the 16th the enemy's artillery was somewhat annoying. At 5 P. M. the 1st Battalion was ordered to relieve the 4th Infantry in guarding the Antietam Creek bridge. This position was held until about noon of the 17th, when a force of cavalry and horse artillery was crossed. This drew a heavy fire from the enemy's artillery. The fire of sharpshooters being annoying to Tidball's battery, a skirmish line was thrown out under Captain Frederick Winthrop, which soon drove them back. Shortly after, the battalion was advanced in support of the battery. About 7 P. M. orders were received to [re]join the brigade [on the East bank of the Antietam].

The loss was 1 killed, and 3 wounded. The 2d Battalion was held in reserve during the entire action, and suffered no loss. General Alfred Pleasanton, commanding the cavalry division, spoke in high terms of the services rendered by the regular battalions in supporting his horse artillery. "

Detail Map #11: Sykes' Regulars Advance from the Middle Bridge (noon-4 pm)
Detail Map #14: Sykes' Regulars Near Sharpsburg (4-5 pm)

Tablet #22: Sykes' Division, Fifth Army Corps - 15 Sep, 2 PM to 16 Sep, 12 PM
Tablet #33: Fifth Army Corps - 15 Sep, 2 PM to 16 Sep, 12 PM
Tablet #87: 4th US and 1st Battalion/12th US Infantry - 16 Sep, 7 AM to 17 Sep, 12 PM
Tablet #88: First Battalion, 12th US Infantry - 16 Sep, 7 PM to 17 Sep, 6 PM
Tablet #122: Army of the Potomac - 17 Sep, 10 AM to 17 Sep, 6 PM
Tablet #121: Army of the Potomac - 17 Sep, 8 AM to 17 Sep, 6 PM