The correct answer is C) there were opportunities to get free land in the West.
The factor that encouraged Americans to move to the West in the 1800s was that there were opportunities to get free land in the West.
After the Louisiana Purchase of 1803, US President Thomas Jefferson ordered the Lewis & Clark expedition to the western territories. When the expedition ended, Lewis went to Washington D.C, to inform the President about the results. That is when Jefferson authorized the settlement of the western territories as part of the fulfillment of the Manifested Destiny. Indeed, the west offered many natural resources and land.