The Oregon Trail was a vital passage to the Pacific Northwest Territory. 
The first wagon train set out on the long trail across the plains and
through the Rocky Mountains in 18411; by 1845 more than five thousand
pioneers had made the journey.  Travelers along the route were constantly
harassed by angry Sioux.  Colonel Stephen Kearney confronted the Indians,
bringing both gifts to placate them and artillery to intimidate them, but
without success.  It was not until 1848, when the first of several forts 
was built along the Oregon Trail, that the Indians discovered the lengths
to which the army would go to ensure an American presence in the
northwest.