it had allow more ways to trade and transport people
<span>American settlers took their land</span>
<span>"worked for the Union army as a nurse, a cook, and a spy. Her experience leading slaves along the Underground Railroad was especially helpful because she knew the land well. She recruited a group of former slaves to hunt for rebel camps and report on the movement of the Confederate troops."</span>
I believe it was "<span>overpopulation."</span>