OMG, this is amazing! The writing is superb, I'm going to have to look into reading Holzer's other work. He's very articulate here and yet says so much in few words and does it without being dry or boring at all.
The objects have been very well chosen and do manage to tell the larger narrative while the actual objects and stories come from New York. Of course, New York - both the city and the State - experienced some unique moments during the Civil War and those have been handled well.
Also, I don't normally build a soundtrack or anything while reading, but listening to the music from Ken Burn's The Civil War documentary has been a perfect pairing!