Today I stumbled upon a website with quite a large collection of old photos from the 19th century and really early 20th century. The site contains several collections, including a Civil War collection and an Old West collection.
A couple of my favorites come from the Civil War collection and are posted below:
I really like this photo of President Lincoln at Antietam because shows Lincoln in a semi-private moment which is a rarity among the photographs taken of President Lincoln during his presidency.
I suppose I like this one for more morbid reasons. Perhaps because it shows a darker side of the war.
In any case, I would take a look through the collection of old photos, located here: http://www.old-picture.com. There is also a blog that goes along with it that I would also take a look at.