The Grounders or Outsiders (by the Mountain Men) is a term used to describe a person who was born on Earth rather than in space or Mount Weather. The Grounders alive today are descendants of humans who survived the Nuclear Apocalypse 97 years ago. Many of the Sky People have negative views toward Grounders, just like a lot of Grounders have a negative view of the Sky People. They were the primary antagonists of the first season.