You can find specialty dealers that sell old wood. A new piece of pine is not going to match a 100 year old one.The old stock is much harder than new growth as well.

If your going to carpet the stair go to a lumberyard (not HD or Lowes) and purchase a piece of stair tread.

Most lumberyard stair treads are 1&1/8" thick.

Two by lumber is 1&1/2" thick.

Using a different thickness tread on one step could easily create a tripping hazard.

Go to a lumber yard and ask them to find(cut) you a piece of wood---inexpensive oak or ash or poplar) to the correct length/width/thickness.

They will charge extra, but it will be the correct size replacement.

handymac, your correct I missed that. The other option would be to get the 1 1/8" stock and have it run thru a thickness planer which if planed off the bottom surface would leave you with the nose intact.

I suspected and confirmed that the 1/16 inch difference is due to the changing standards in nominal lumber sizes. A 1x10 was 13/16 until 1910.

I will make the replacement tread from 1x10 select pine.

Your comments were interesting. Thanks.

If this is a "housed" stair, meaning that the treads actually extend into the stringers, you can't replace a tread from above, it has to be replaced as it was assembled, from the underside/back.
Casey