hardwood floor stains

m0nguse

I purchased my childhood home (built in 1959) from my parents and I just ripped the carpet up to display the hardwood floors; these are REAL hardwood floors, OAK I believe). Upon removal of the carpet/padding there are several black spots on the floor, presumably from pet urine. I plan to have the floors sanded and refinished with polyurethane. How do I get rid of these black marks; they have been there for several years...since there hasn't been pets to urinate in the home since 2004ish.

I've read about using peroxide or chlorine bleach and even baking soda but I don't know...the marks are really dark. I'm hoping the boards don't have to be replaced.

Does anyone know if homes built in 1959 would have had the hardwood floors polyurethaned or just waxed; how would you find out?

My home is in northeast Ohio, if that helps...since different regions may have used different procedures.