Final answer:
Marcus Whitman was an important figure in the settlement of Oregon, establishing a mission that helped bolster U.S. claims to the territory during a time of westward expansion and heightened U.S.-British competition over the region.
Step-by-step explanation:
Marcus Whitman was a significant figure in the settlement of Oregon. As an American missionary and physician, he, along with his wife Narcissa, established the Whitman Mission in present-day Washington State with the aim of converting the Native American population to Christianity. Their efforts were part of the greater movement of westward expansion that was fueled by "Oregon Fever" and the national ethos of Manifest Destiny, which encouraged American settlers to move west. Their presence, along with the mission, promoted further American migration, bolstering U.S. territorial claims against British Columbia, particularly given that the U.S. and Great Britain were in contention over the Oregon Territory.
While not directly mentioned in the provided materials, Marcus Whitman's role also included his tragic death, which resulted from conflicts between settlers and Native Americans, an event that dramatically impacted perceptions of the region and relations with Native Americans.