[Minor edits 12/25/09]
Two days after the battle of Cowpens, the American commander, Brigadier-General Daniel Morgan, wrote the following report of his victory to his superior, Major-General Nathanael Greene.
"Dear Sir: The troops I have the honor to command have gained a complete victory over the detachment from the British Army commanded by Lieut.-Col. Tarleton. The action happened in the 17th inst., about sunrise, at the Cowpens... An hour before daylight one of my scouts returned and informed me that Lieut. Col. Tarleton had advanced within five miles of our camp. On this information, I hastened to form as good a disposition as circumstances would admit, and from the alacrity of the troops, we were soon prepared to receive them. The light infantry, commanded by Lieut. Col. Howard, and the Virginia militia under the command of Major Triplett, were formed on a rising ground, and extended a line in front. The third regiment of dragoons, under Lieut. Col. Washington, were posted at such a distance in their rear, as not to be subjected to the line of fire directed at them, and to be so near as to be able to charge them should they be broken. The volunteers from North Carolina, South Carolina, and Georgia, under the command of the brave and valuable Col. Pickens, were situated to guard the flanks. Maj. McDowall, of the North Carolina volunteers, was posted on the right flank in front of the line, one hundred and fifty yards; and Maj. Cunningham, of the Georgia volunteers, on the left, at the same distance in front, Colonels Brannon and Thomas, of the South Carolinans, were posted on the right of Maj. McDowall, and Cols. Hay and McCall, of the same corps, on the left of Maj. Cunningham. Capts. Tate and Buchanan, with the Augusta [Virginia] riflemen, to support the right of the line.
"The enemy drew up in single line of battle, four hundred yards in front of our advanced corps. The first battalion of the 71st regiment was opposed to our right, the 7th regiment to our left, the infantry of the legion to our centre, the light companies on our flanks. In front moved two pieces of artillery. Lieut. Col. Tarleton, with his cavalry, was posted in the rear of the line.
"The disposition of battle being thus formed, small parties of riflemen were detached to skirmish with the enemy, upon which their whole line moved on with the greatest impetuosity, shouting as they advanced. McDowall and Cunningham gave them a heavy and galling fire, and retreated to the regiments intended for their support. The whole of Col, Pickens' command then kept up a fire by regiments, retreating agreeably to their orders. When the enemy advanced on our line, they received a well-directed and incessant fire. But their numbers being superior to ours, they gained our flanks, which obliged us to change our position. We retired in good order about fifty paces, formed, and advanced on the enemy, and gave them a fortunate volley, which threw them into disorder. Lieut. Col. Howard observing this, gave orders for the line to charge bayonets, which was done with such address that they fled with the utmost precipitation leaving their fieldpieces in our possession. We pushed our advantage so effectually, that they never had an opportunity of rallying, had their intentions been ever so good.
"Lieut. Col. Washington, having been informed that the Tarleton was cutting down our riflemen on the left, pushed forward, and charged them with such firmness, that instead of attempting to recover the fate of the day, which one would have expected from an officer of his splendid character, broke and fled.
"The enemy's whole force were now bent solely in providing for their safety in flight-the list of their killed, wounded, and prisoners, will inform you with what effect. Tarleton, with the small remains of his cavalry, and a few scattered infantry he had mounted on his wagonhorses, made their escape. He was pursued twenty-four miles, but owing to our having taken a wrong trail at first, we could never overtake him.
"As I was obliged to move off of the field of action in the morning, to secure the prisoners, I cannot be so accurate as to the killed and wounded of the enemy as I could wish. From the reports of an officer whom I sent to view the ground, there were one hundred non-commissioned officers and privates, and ten commissioned officers killed, and two hundred rank and file wounded. We now have in our possession five hundred and two non-commissioned officers and privates prisoners, independent of the wounded, and the militia are taking up stragglers continually. Twenty-nine commissioned officers have fell into our hands... The officers I have paroled: the privates I am conveying by the safest route to Salisbury.
"Two standards, two fieldpieces, thirty-five wagons, a travelling forge, and all their music are ours. Their baggage, which was immense, they have in a great measure destroyed.
"Our loss is inconsiderable, which the enclosed return will evince. I have not been able to ascertain Col. Pickens loss, but know it to be very small.
"From our force being composed of such a variety of corps, a wrong judgment may be formed of our numbers. We fought only eight hundred men, two-thirds of which were militia. The British, with their baggage-guard, were not less than one thousand one hundred and fifty, and these veteran troops. Their own officers confess that they fought one thousand and thirty-seven.
"Such was the inferiority of our numbers that our success must be attributed, under God, to the justice of our cause and the bravery of our troops. My wishes would induce me to mention the name of every sentinel in the corps I have the honor to command. In justice to the brave and good conduct of the officers, I have taken the liberty to enclose you a list of their names from a conviction that you will be pleased to introduce such characters to the world."
This is clearly an important document pertaining to the battle. Probably the most important document. Morgan was the architect of the victory, he was able to view the entirety of the battle. In the 2 days since the end of the battle, he had time to replay the events of the day in his head and confer not only with his officers afterwards, but with those of the enemy that became his prisoners. The events of the day were no doubt very clear to him; clearer certainly than participants writing about the battle many years later. It was also imperative for him to get the account right. His description of how the battle was fought and won would likely influence the behavior of other American commanders in future engagements.
John Moncure's online history of the battle, The Cowpens Staff Ride and Battlefield Tour, includes a transcription of Morgan's report.
James Graham's (1856) The Life of General Daniel Morgan also has a copy of his report, including an appendix naming many of the officers that fought at Cowpens.