Thanks for your help so far. I figured this might have been an older rifle. It may have even been handed down to him. I am also aware that gunsmiths would often make rifles on a local basis. (I live near Great Smoky Mountains National Park, and several local gunsmiths have been well documented during this same era.)
Here are a few more hints: Charles Ingalls was born in Cuba, Allegany County, New York, in 1836, and his daughter, Laura Ingalls Wilder, was born near Pepin, in Pepin County, Wisconsin, in 1867. Charles Ingalls had a younger brother who fought in the Civil War, but I believe he may have been the only one who fought in that war (and it changed him for the worse, apparently).
These books were written as memoirs.
Little House in the Big Woods was published in 1932, when Laura Ingalls Wilder would have been about 65 years old. I imagine many of her memories were blurred and/or combined. In
Little House, she would have been only 4 and 5, during the full year recorded in the book. I am just looking for a general rifle her father
might have carried (but if someone could somehow figure out the exact rifle, I would LOVE it, of course).
Here's how I am planning to use this information: I am thinking of making a two-dimensional model of it by enlarging an image, printing it, and mounting it to stiff paper (with, maybe, a paper fastener for moving the hammer), so I can sort of model "Pa's" method for cleaning it. (The books keep flopping closed when I stand them, showing long, two-page illustrations on my knee.)