1956
Indeed the modern professional version was invented and put into the forestry market in 1956 by Vermeer. Previous attempts used back goes or manual axe and or Maddax for removal!
It is amazing that this tool has been out as long as it has and I still am in total education mode trying to tell people what it is and how it works!
Regardless stump grinders are really cool pieces of equipment especially when they are remote controll like my Carlton 7015 They have sure come a long way!