This is rather lengthy, but William A. Armstrong gave an in-depth description of the activities of William McKinley and the 23rd Ohio Volunteer Infantry at Antietam in his book “Major McKinley: William McKinley and the Civil War”. Kent, Ohio: Kent State University Press, 2000.
P38-41: “The supply train for the ninth Corps had not come up before the battle began, and the men had gone to their battle positions at 2:00 A.M. without breakfast and with no rations in their haversacks. By 2:00 P.M., the men of the 23rd Regiment, lying in a sheltered position across the Antietam awaiting orders to advance towards Sharpsburg, were exhausted and famished. McKinley, who was acting commissary officer for his brigade, was aware that his regiment was awaiting orders to move forward again and was determined to feed the men. Without consulting anyone, he went back to the wagon train and the commissary stores two miles behind the battlefield, gathered up the stragglers, and put them to work preparing rations. Then he loaded a wagon with cooked meat, pork and beans, crackers, and a barrel of ground coffee and asked for a volunteer to go with him to get the food to the men.
John A. Harvey of Company I volunteered to go with McKinley and later described their ride to the front.
We started by the way of a by road through a heavy piece of woods. After driving along the road for some distance from the camp, we met an Army officer with his staff and he told (then Sergeant) McKinley that he must not try to go to the Regiment as it would be impossible to run the blockade, as the Rebel forces had command of an open strip in the woods. The road being so narrow that we could not turn around Sergeant McKinley thought we had better try to go on a little farther. Before we came to the open space in the woods, and close to the brow of the hill we met another Commanding Officer who ordered us to immediately turn back. We stopped and considered the matter and the Officer and his body guard went in the opposite direction. This left Sergeant McKinley to decide what was best to do. The Regiment was almost in sight of us and Sergeant McKinley was so anxious to carry out his point and give the half-starved boys something to eat. He made one more appeal to me to run the blockade, he himself risking his life in taking the lead, I following and the horses going at full speed past the blockade. We had the back end of the wagon shot away by a small cannon shot. In a very few minutes we were safe in the midst of the half-famished regiment.
The soldiers in McKinley’s regiment noticed an army wagon approaching from the rear ‘at breakneck speed, through a terrific fire of musketry and artillery that seemed to threaten annihilation to everything within its range.’ When the wagon drew up, they saw that it was McKinley, who leaped from the wagon and reported his arrival to Major Comly (commanding of the 23rd Regiment after Lieutenant Colonel Hayes was wounded). Colonel Scammon, hearing men cheering on the left of his line, sent Lt. James Botsford to find out the reason. Botsford found both officers and enlisted men cheering McKinley and the hot rations he had brought them. The men fell back to the wagon in groups of ten to receive their share. One man who had been severely wounded in the battle was heard to murmur, ‘God bless the lad!’ After the war, McKinley liked to say that those words ‘were the highest reward that he could possibly have received’ for what he had done.
The 23rd’s casualties at Antietam were less than at South Mountain, although they were severe enough: eight men were killed, fifty-nine wounded, and two missing. The regiment’s losses at the two battles created vacancies among the officers, and Major Comly, impressed with McKinley’s actions, recommended him for a promotion. He wrote to Hayes, who was recuperating in Ohio, that McKinley ‘showed ability and energy of the first class in not only keeping us fully supplied with rations throughout the fight, but in having them fully prepared for eating, also. We had plenty when everybody else was short. He delivered them to us under fire, in two instances, with perfect method and coolness…. I feel greatly indebted to McKinley. No promotion could be made which would give more general satisfaction.’ McKinley, too, was thinking about a promotion. Hayes’s brother-in-law Joseph T. Webb, who was a surgeon in the 23rd, also wrote to Hayes: ‘Our young friend McKinley [,] Commissary Sergeant, would be pleased with a promotion, and would not object to your recommendation for it. Without wishing to interfere in this matter it strikes me he is about the brightest chap spoken of in the place.’ Thirty-four years later, some of McKinley’s comrades sought a greater recognition for him: The Congressional Medal of Honor. Shortly after McKinley’s election to the presidency, they appealed to President Grover Cleveland to award the medal, and Nelson Miles, the major general commanding the army, recommended the award, but when McKinley learned about it, he asked that no action be taken, and the matter was dropped. Two years after McKinley’s death, the state of Ohio erected a thirty-three and a half foot monument near the Burnside Bridge on the Antietam battlefield to commemorate McKinley’s ‘valiant act’ during the battle.”