White Oak
It is an oak of some type for sure. Then one bark pic is what is confusing. The bark looks more like pin oak but if that is off a limb and not the truck it could be white oak. Generally white oak bark has large lose fitting flakes and pin oak has bark like a red oak but with some flaking. Also any pin oak that I have split has a darker heartwood than anything in your pictures. The other possibility is water oak as the bark looks just like that, but you are a little far north for water oak although it could have been transplanted. If it was water oak you would have noticed the smell for sure, till it seasons it smell like cat pee. Also as the name implies, water oak is very wet then green and will be very heavy. White oak will also weigh more than red oak. Since you mentioned how hard it was to split I will go with white oak as I find it to be the only oak that puts up much of a fight splitting.