The Giving Tree

Do you remember the wonderful story by Shel Silverstein, The Giving Tree?  We have a real-life Giving Tree just beyond our backyard.  I'd love to know how old this Maple is, perhaps 100 or 150 years old?  It's nearing the end of its life, but in just the relatively short time we've been witness to the tree, it's given many times and not just to our family.
A treehouse:

Stacking rounds and craft medium for Kari and Bryce at school:

Sadly, a dumping ground:

And most recently, firewood:

Dad brought his chain saw down this weekend in hopes of some mild weather.  We had a wonderfully warm 50F Friday and cut up many of the downed branches that had fallen during some recent wind storms.  Kari stayed home on Friday and even got to cut her own log with the chainsaw.  The tree is not on our property, so I think technically we were trespassing, but nobody stopped us and we went about our business.  This morning I brought the logs back to our property and attempted to stack it.  We're already looking forward next winter to some nice dry firewood from our very own Giving Tree.