Answer: B) Americans trying to settle on the west coast.
The Oregon Trail was a 2,170-mile long wagon route and emigrant trail that connected the areas around the Missouri River to the valleys in Oregon. It spanned part of modern-day Kansas, most of Nebraska and Wyoming and most of Idaho and Oregon.
It was used heavily during the second half of the 19th century by settlers, ranchers, miners and farmers. The use of the trail declined with the construction of the first transcontinental railroad, completed in 1869.