Is the tile on top of the wood floor or is there plywood between the wood floor and the tile? Or is that vinyl flooring between? Hard to tell from the picture but it looks like mastic.

If there is any chance that was put down before 1980, the VERY first thing I would do is get it tested for asbestos.

If no asbestos, and it is mastic, it can be sanded off.

Hi, Marti!
From top to bottom we have: tile/mastic, linoleum, plywood, black/dirty goo, hardwood.

I hadn't thought of asbestos. I'll look into that.

I think I'd either ask on the remodeling or old house forum, or find a construction forum somewhere else. There might be another way to remove it that doesn't involve sanding.

I removed black goo from my pine floors by covering the area with wet rags for a few days. Then I was able to wipe up most of it, scrape the rest. I had similar layers in a 1930s house. Your goo may be different from mine however. Good luck!

Thanks for the tip, Maureen! I also read on the reno board that a steamer helps. I never would have thought of that.