The answer is: Western settlement increased because American Indians were forced off their lands.
During the war of 1812, the American Indians had to face the coalition of both British and Spanish empire. They had no chance of wining. After suffered heavy loss, the american Indians were forced to migrate from their ancestral land.
This made the land become unoccupied. Many people from across the world see this as opportunities to settle in that area and bought up land to open new businesses.
