This letter was written by a member of the Army of the Potomac, most likely a lieutenant in a Massachusetts or New York Regiment. My best guess would be the former. His ranking officer was “Captain Carpenter” but I have not yet been successful in identifying one by that name from a unit to match the regiment’s movements. From the letter we know that the author’s regiment crossed the Potomac River on the morning of 19 July 1863 and he informs his wife that his regiment was “in the rear of the whole army.” The Army of the Potomac crossed the Potomac River at Harpers Ferry and Berlin (now named Brunswick) on July 17, 18 and 19th. They advanced southward through Loudoun Valley on the east side of the Blue Ridge Mountains, trying to interpose themselves between Lee’s army and Richmond.
After crossing the Potomac, we also learn from the letter that the author’s regiment marched 10 miles south before halting, and they planned to march another 20 miles the following day toward Warrenton, no doubt.
The author signed his name “Will” and wrote with a pen stroke suggesting a good education. If the author was from the Boston area, his wife may have previously been visiting relatives or vacationing in the vicinity of Warrensburg, New York.
[Note: This letter is from the personal collection of Jim Doncaster and is published by express consent. The header image is a painting by Forbes of the “Pursuit of Lee’s Army.”]
Virginia, 10 miles south of Potomac
July 19 
My Darling Wife,
Here I am once more on the sacred spoil of Virginia. We crossed this morning [and] are in the rear of [the] whole army. Don’t know where we are bound for but don’t think [we] shall do much at present but get between Richmond & Washington and wait for the conscripts. Three captains and six sergeants start tomorrow for them. They are going to fill up the old regiments instead of forming new ones and a good idea it is for we can make good soldiers of them in quarter the time that could by forming new regiments of them. Captain Carpenter is going so I am left in command of the company. If you were in Boston, I would have [him] call on you. If we go into camp again, perhaps I can get north before the fall campaign opens. Shall try at all events.
The river is full of dead Rebs & wagons &c. swept away when they forded. Lee goes out of Maryland 40,000 men worse off than when he came in now. I think it was a grand mistake not attacking him the day before he crossed as we started to. But perhaps it is better as it is. I think the southern confederacy is pretty much gone up. They may be one or two more big fights but the heaviest fighting is over. They cannot raise many more large armies though they may hold out for a long time yet. We have only about 10 months longer to stay and that will soon be gone, my darling, and then we won’t be separated again.
I haven’t got over my neuralgia yet and it doesn’t improve my looks or temper a bit. Write me all about what kind of a time you are having. I expected a letter from you last night but didn’t get one. Your last was dated the 6th. I enclose a photograph of young Carter. He is the one that drew those sketches in my diary and those photographs were taken from his sketches. But I suppose you haven’t seem them as they were sent to Warrensburg. Don’t tell Frank or Cary about that baby. Please tell Brig. if you see him to write me. I wrote last and its much easier for him to write than me as my knee has to serve for a desk. I have to cut this paper in two to get it into my haversack.
Now darling, do write often as you can for your dear letters are all I have to cheer me up. My face aches terribly tonight and I do wish that I could be with my better half. I’ve a fancy you could stop the pain. It’s hotter than —- a good deal and we have got to travel 20 miles tomorrow so I must retire. So goodnight, darling.
Yours affectionately, — Will