I will agree with the general consensus that it is a type of pine. Definitely NOT maple... In the 1880's the wood that was used in homes would be something taken from the area usually a longleaf pine, also called heart pine, and there was an abundance of white pine too, although it is much more softer than heart pine or ponderosa pine that was used a lot on the east coast.
Any pine product used for wood floors is not the best choice, but with availability and possibly cost, it was used in many many homes back then and well into the 1900's. It is a much softer wood than many other choices of specie that would have been locally available. Oak, Black walnut, maple and a few others come to mind that are much more dense (resistant to damage) than any specie of pine grown in that area or region.
Now onto the actual type of pine.The pictures you present tell me it is a white pine, but there are more things needed to be known before that can be confirmed, like the smell when cutting it for example... hard for me to do from here. The thickness of the floor may help too and if it is T&G as Lee Sam suggests, In my experiences, in old homes such as yours, the floors can face nailed originally, and not necessarily T&G. Sometimes the flooring is much thicker, 7/8" thick or more. Wood was plentiful back in those days. I have not seen a old home done in white pine, but many that were done in heart pine and ponderosa pine, but that wood has a slightly different look about it, and the hard and soft wood of the annular rings have more contrast. The darker grain is much more harder than the lighter soft wood. In white pine the annular rings have the dark (hard) and light (soft) same as the heart and ponderosa pine, but the density of the rings/grain is more consistent between the hard and soft rings, making it the least desirable of the choices of pine. A simple test I failed to mention earlier was that you can take your thumbnail and press it into the wood across the dark and light rings and it will leave an impression, a small one, but it will leave one. Something not so easily done with oak, maple or on the dark rings only of ponderosa pine or heart pine.
Just another mention, you thought the floors have never been refinished, they have. The score mark across the wood in one of the pictures tells me it has been. When the finish or stain gets into a cut like that, it darkens that way. If the cut occurred after the finish was applied, the cut would be much lighter. Sanding may remove the cut so it will finish out well. Another note, if the floor is white pine which I think it is, and the builder knew how soft that floor is, the flooring may have been cut thicker to allow for more refinishing over time.