For decades, researchers believed early humans first settled in the Western Hemisphere around 13,500 years ago. However, the discovery of 150,000 'unique' stone tools northwest of Austin, Texas, now suggests humans were living on the continent as far back as 20,000 years ago

See the source article by following the link below:
For decades, researchers believed early humans first settled in the Western Hemisphere around 13,500 years ago. However, the discovery of 150,000 'unique' stone tools northwest of Austin, Texas, now suggests humans were living on the continent as far back as 20,000 years ago