It's pretty hard to identify, with any certainty,
the rifle with the pictures you have supplied here. I will say that it appears to be of small caliber... most likely .36. It is a rifled barrel rather than a smooth bore.... and has a set trigger for accuracy. These type of rifles were built and used for hunting and gathering food for survival.... but of course also used for protection. These were manufactured by quite a few craftsman in the Pennsylvania/ Connecticut area during that era..... The smaller calibers were used mainly as small game hunting calibers because frankly the smaller calibers used less lead and gun powder And those two items were at a premium on the frontier.
It would not have been really a preferred battle weapon in the civil war... but that's not to say it was not used.
Cool original piece of American firearm history for sure.
Typically... somewhere on the barrel by the breech end or on the lock would be an engraving of the name of the craftsman who built it.... and perhaps the location like Lancaster Penn. etc.