Great image. He is a very earnest looking fellow. Of course, most soldiers look so serious because they have to hold their pose for about ten seconds or so. Exposure times were so long that photographers provided stands that could hold your head still. This fellow's eyes are quite intense.
I hope some of our uniform experts comment because the stiff collar is nice and the piping on the uniform is very distinctive. I would say it is a Federal Infantry Frock Coat. However, I am no expert like others here.
I enjoy collecting historic photographs, particularly soldier images, but civilians as well. For me they boil the grand sweep of history down to a single individual - a person, just like us who wakes up in the morning, gets dressed and experiences the trials and tribulations of life just as we do. History becomes about all the individual people that actually participated in it. You can see what they were wearing, look into their eyes and maybe, just maybe get a sense of who they were.
We studied history in school and unless we were lucky enough to have a fantastic teacher, history is just famous names and lots of dates to memorize. We live in a time where swiping on our phones is our most important activity and too many people that I talk to simply glaze over with that lost, vacant look when I talk about history. They are thinking, "boring...." When holding a photograph like yours you are not only seeing the individual, but you are also holding something that was actually held by someone over one hundred and sixty years ago. Unlike a picture in a book, it is a direct connection to the past. I can imagine the soldier posing, getting that cased image and giving it to a loved one. It was a cherished treasure to someone. I have seen people clearly bored with history light up and get fascinated when they hold an image like yours; it can be like magic.
Enjoy!