The marker for the Ninth Army Corps – September 15-16 is on the east end of Burnside’s Bridge, next to the Ninth Army Corps – September 17 marker, on which the story of the Ninth corps at Antietam continues. (Burnside’s Bridge tour map) 

From the marker:

U.S.A.

Ninth Army Corps

Brig. Gen. Jacob D. Cox, Commanding.

September 15-16, 1862.

The Ninth Army Corps moved from Fox’s Gap in South Mountain by the Sharpsburg Road on the morning of September 15th, and in the evening encamped in the rear of the extreme left of the Army of the Potomac under the crest of the ridge opposite the Middle Antietam Bridge.

On the morning of the 16th the Corps moved to the left and took position upon the rear slopes of the ridges on the east bank of the Antietam, the center nearly opposite the Burnside Bridge.

Benjamin’s Battery (E, 2nd U.S. Artillery) occupied the knoll commanding the bridge; the remaining Batteries of the Corps were in reserve under cover of the ridge. During the 16th Benjamin’s Battery engaged the Confederate Batteries posted on Cemetery Hill.

In the afternoon the Battery moved a short distance south; Crook’s Brigade on its right rear, supported by Sturgis’ Division, and Rodman’s Division on its left rear with Scammon’s Brigade in support. Wilcox’s Division formed a third line in reserve.

No. 56.