How did missionaries like the Whitman's help other people to settle in Oregon?

Answer 1

From Wikipedia:

The Oregon missionaries were collectively the religious-minded pioneers who settled in the Oregon Country of North America starting in the 1830s with the intent of converting local Native Americans to Christianity.

Answer 2

The Oregon Country was a predominantly American term referring to a disputed ownership region of the Pacific Northwest of North America. The region was occupied by British and French Canadian fur traders from before 1810, and American settlers from the mid-1830s. The Native population eventually shared the same marginalized fate as the rest of the Indian tribes.

Answer 3

The Whitmans built their mission near the Columbia River and began to work with Cayuse Indians, setting up a mission school and a clinic. Soon, other missionaries and settlers joined them.