Google images couldn’t help me out. I found no image that resembles what this guy is wearing.
I’m guessing Union, because it looks as if his uniform is Union blue.
Perhaps, but maybe the photo just turned out dark. Photography wasn’t so good back then.
I was hoping someone would recognize the hat or the epaulettes.
IIRC (from reading, not from being there!) some Confederates did have blue uniforms at one time or another, which would confuse matter further. But I don’t know if I do recall correctly, nor how widespread it was if such was the case. As for the hat, it appears to be a kepi of some sort. (I’d have to find my Dixie Gun Works catalogue to see the different styles, as they may have had different names.) Both sides wore kepis. Epaulettes too.
Is that your own picture? If so, can you shoot another digital at a different angle (the glare is a li’l tough). Heck, even better, can you scan the old photo?
Tripler
I might have a lead. . .
If so you have lived a remarkably long time 
The background is lighter than the uniform. The skin is lighter yet, the epaulets even lighter, and the buttons seem bright. I don’t see how a case can be made that the uniform alone is deceptively darker in the photo than it was on the subject. Everything else appears as one would expect. I think it’s a safe bet to say it’s a Union uniform.
There was a confusing variety of Confederate uniforms (and I’m certainly no expert on the matter), but the only blue ones I’m aware of were light blue - lighter than the well-known gray. I’ve never seen any illustration of a Confederate uniform as dark as the one in the photo.
That could be what I was semi-remembering. Still going for Union on the photo.
Not to throw a monkey wrench into the proceedings, but are you sure it’s a U.S. Civil War soldier to begin with?
Zev Steinhardt
I’ll see if I can take a better photo of this over the weekend, w/o so much glare.
Although I must say, the comments by Gary T have got me thinking Union, too.
Zev, I was told that this was a U.S. Civil War soldier by a reputable (but of course not infallable) source. I welcome the comments of any SDMB experts who might say otherwise.
Where is that picture from? That looks very very familiar to me, but I have no idea why.
Not matching the uniform, but I did find this which seems to be a very similar frame.
Confererate junior officer uniforms had a single row of seven buttons, and Union junior officers had a single row of nine. This one has eight showing.
Am I misremembering when I think that navy blue shows up as white in black and white photographs?
Yes.
I could swear that my mother showed me pictures of herself as a child that were black and white, and the dress that looks greyish white in the photo was really navy blue. Are you certain? 
Why would it?
If you’re shooting with a blue filter or with a film that is exceedingly sensitive to blue, then you may have navy blue show up lighter than normally it would. However, unless it’s really overexposed, navy blue ain’t gonna come out white.
Well, either it’s a very well entrenched UL that has somehow permeated my memories (Which I am willing to see is possible.) and I need to “weed” or it is true. Can anyone find a cite that proves either way? At this point my memories of looking at that picture are still winning out.
Your memories may be correct, but your mother’s memories that her dress were navy blue may not be. Do a Google images search on “union soldier” and you’ll find plenty of black-and-whites that confirm this.
Except that it was her favorite dress, and her sister recalled it was navy blue too. I found something about cheap film rendering navy blue lighter, maybe the film was cheap?
Off the top of my head, I can think of regiments form New York and New Hampshire that outfitted their troops in gray, while there were troops from Georgia and Louisiana that wore blue. the word “uniform” is really a misnomer when talking about the Civil War. Google “butternut” or “zouave” and see.
While epaulets were not unknown on Confederate uniforms, they were more likely to indicate rank by the degree of elaboration in the Turkish braid on the cuffs. Also, Confederate kepis were more likely to have a quatre-foil embroidered on the top.
But I’m not sure and, in case the OP is waiting to spring the answer on us, I’ll avow certainty.