Redfish, I don't think it is magnolia. I have a magnolia tree in my front yard and I am looking at it right now. The bark is a LOT darker and if this is ther right expression coarser. It is also somewhat thicket than what the pictures appear to show. You usually don't see as much straightness to the outside of Magnolia, as it tends to send off small branches and shoots almost from the ground up, or at least mine does and it is about the same diameter 16-20". You may be right on the Honey locust, right coloring and bark, but is the growth rings as pronounced as shown in the pics? That I am not sure about.
Rob