The 27 states responsible for ratifying the 13th included 8 of the 11 CSA states (Georgia actually put it over) and 19 of the 25 on the Northern side of the fence, which makes the ratios as close to equal as possible given the numbers we are working with.
http://13thamendment.harpweek.com/HubPages/CommentaryPage.asp?Commentary=05Results
Ratifying the 13th was a condition for readmission to the union.
They ratified it in the sense that the Mafia gives someone a deal they can't refuse. They ratified it at the point of union guns. Our legal system doesn't believe in coercion or duress unless it comes from the very top, then they are all in favor of it.
Does anyone really believe that those Southern states actually ratified the 13th amendment of their own free will? If so, I have a bridge in San Fransisco that i'd like to sell you.