Welcome! I must confess, I am not familiar with that one, but I hope someone who does know sees this and can help you out!
It would most likely help if you gave us your G G grandfather's name and what state he was from.
OK, I found it.
Ive had this image for some time and was thinking about selling it. The soldier is wearing a buckle that says Washington Rifles. I did a bit of research and found that this was a NY militia unit during the Civil War (which makes sense as the photo was taken in NYC). His kepi insignia has the numb...www.usmilitariaforum.com