Hello and Happy Thanksgiving!

I just closed on my first house and the upstairs carpet was nastier than I remembered....so we now have cleaner, though worn, hardwood.

The house, in Lancaster County, PA, was built in 1910. I'm going to try my hand at replacing a couple of boards and refinishing the entire second floor.

Can anyone help me identify what I've got?

https://flic.kr/s/aHsmXf9pTm

Thank you!

This looks like VG Douglas fir. That is vertical grain Douglas fir. New wood flooring is probably not going to match the sameT&G spec's. Find some old wood somewhere if you can. This flooring is used for the sub-floor and finish floor in most old homes, just one layer. If you need to patch it's best to end the board over a joist, but if you can glue a piece of plywood underneath with sub-floor adhesive and let it set up before the patch then you could make a joint where you want. You would need to use C-clamps while the glue hardens.
When you are looking for a piece of flooring for a replacement, take a piece of what you have to check the T&G. It's important that they match since it is usually just one layer thick with no sub-floor.

Thank you, Pete A.! That makes a lot of sense now....I've been wondering why, when I can see through some gaps between boards, I can see no subfloor.

Here are a few more photos of some of the refinish work: https://flic.kr/s/aHsmXf9pTm

Does this give a more positive/absolute identification? The floors are certainly aromatic.

Thanks, again!

Any recommendations on what stains/colors work well with VG Douglas Fir? I'm thinking we'll do Rubio Monocoat 2c and was originally going to keep it pure, but am now thinking the floor is brighter than I thought it would be.

This floor is not vertical grain Douglas fir. It looks like a pine floor. There are different species of pine that it could be. Some pine is harder than fir. This floor was probably made from a locally grown specie. I am not familiar with this specie.
The old finish may have been a colored shellac for a seal coat, then a varnish with linseed oil, which tends to turn brown over time. Poly-urethane will have a yellow color.
I think a pigmented color like Zar stains contain will look best. Popping the grain with a pretreatment of a coat of plain water to raise the grain after the final sanding will allow more stain to penetrate when applied after the water has dried.
This can also help to diminish some scratches left from sanding. Making a sample in an inconspicuous area before staining the whole floor is a good idea to help with color selection.
Do you have a Habitat for Housing store in your area? They could have some of the old floor that' being recycled.