The correct answer to this open question is the following.
The need for raw materials led to further state expansion, following the Manifested Destiny that was the belief for many Americans that God's will was for America to expand its territories. After the Louisiana Purchase of 1803, US President ordered the Lewis & Clark expedition to the new Western territories. When the exédition was over, those explorers went to Washington D.C. to inform the President about the results. That is when Jefferson authorized people to settle those territories, work the land, and exploit the many raw materials and natural resources to get a profit.