It was the federal military that ended slavery at the cost of over 100,000 (?) US Army soldiers killed in or resulting from combat and tens of thousands others dead from disease. Of course, there were terrible losses on the other side as well and among the civilian population. (And I am not implying that the Confederate soldiers were fighting primarily to preserve slavery.) Not to take anything away from Tubman but if it is all about freeing the Black man, then maybe Sherman or some other Civil War soldier should join Grant on our paper currency.
600,000 soldiers killed (north and south) over the struggle to free slaves.