In the 19th century, Americans who wanted to become missionaries could apply to organizations called “mission boards.” One of the first of these was the American Board of Commissioners for Foreign Missions, or ABCFM, founded in 1810.

“When it was first founded they had kind of a dual idea of mission work," says Emily Conroy-Krutz, a history professor at Michigan State University and author of Christian Imperialism: Converting the World in the Early American Republic. "The way they framed it initially was that they were going to go both west and east. And so, North American missions to Native American peoples [were] part of the agenda from the very beginning."

ABCFM sent its first mission to a British-controlled region of India, but it soon established missions closer to home: it launched a mission to the Cherokees in Tennessee in 1817, and another to the Choctaw in Mississippi in 1818. In the 1830s, it sent the Whitmans and the Spaldings out west, where they established missions among the Cayuse and the Nez Perce nations, respectively.

Different mission boards represented various denominations, but most of the missionaries who went west during this period were Protestant. These Protestants wanted to spread their version of Christianity while actively working to curb the spread of Catholicism, which they often viewed as a rival faith.

To many missionaries, conversion was not just about religious belief. It was also about adopting the same social customs as white Protestant Americans. U.S. missions in the west established schools to convert Native people to Christianity, as well as the missionaries’ ways of living and working.

The school at Jason Lee’s mission “was designed as a manual labor training school,” says Kylie Pine, curator and collections manager at the Willamette Heritage Center in Salem, Oregon. The school taught Euro-American styles of farming, cooking, blacksmithing and other skills that the Methodist Missionary Board believed local Native communities lacked.

These schools served as models for the industrial schools that U.S. missionaries would later open overseas, Conroy-Krutz says. They were also a precursor to the U.S. boarding schools that sought to strip Native people of their language and culture in the late 19th and early 20th century.

Although mission schools were not the same as federal boarding schools, they often imposed similar practices, such as stripping Native people of their names, forcing them to learn English or demanding they abandon their own cultural practices.

U.S. missions often aided the country’s expansion by creating settlements in Native nations at a time when multiple colonial powers were competing for Native land.

"By the time Jason Lee gets here in the 1830s, the United States was nominally claiming every area west of the Mississippi as part of the Louisiana Purchase,” Pine explains.

In addition to the Native nations that had long lived in the region, the overseas empires of Russia, Spain and Great Britain—through its Hudson Bay Company—all had attempted to establish colonial presences in Oregon Country. However, the U.S. missions helped establish permanent settlements in the region, further advancing American territorial claims.

“The Methodist U.S. missionaries who will go to the Willamette Valley…end up also becoming permanent settlers of the area,” says Jacki Hedlund Tyler, a history professor at Eastern Washington University and author of Leveraging an Empire: Settler Colonialism and the Legalities of Citizenship in the Pacific Northwest.

In 1843, U.S. settlers established a provisional government in Oregon Country to strengthen the nation’s authority. This encroachment increased tensions between Native communities and U.S. missionaries and settlers.

Decades before U.S. missionaries arrived in Oregon Country, Native nations in the region suffered waves of smallpox and measles epidemics stemming from contact with European fur traders. When missionaries arrived in the 1830s, they encountered traumatized communities that had recently lost many members to disease, and these experiences influenced how Native people responded to missionaries.

In 1847, a measles epidemic broke out among the Cayuse in Waiilatpu, where the Whitmans had established a mission. The disease disproportionately affected the Cayuse and many Cayuse grew angry that Marcus Whitman, a doctor, seemed unwilling or unable to help them survive a disease that they associated with him and his fellow settlers.

On November 29, a group of Cayuse murdered Marcus, his wife Narcissa and 11 other people at the Whitman mission. This was the start of the Cayuse War, in which the Cayuse fought U.S. settlers and soldiers for control of their homeland.

In 1848, amid the ongoing Cayuse War, the United States incorporated Oregon Country as the U.S. Oregon Territory. With this action, the U.S. government officially claimed the region as part of the United States.

The Cayuse War ended in defeat for the Cayuse, whom the U.S. forced onto a reservation with the Umatilla and the Walla Walla nations in 1855. Soon after, more wars broke out in the Oregon Territory as Native nations fought to remain in their homelands. The Rogue River War ended in 1856 with the forced relocation of many Native people in southwest Oregon to the Coast Reservation (now the Siletz Reservation).

In 1859, the United States admitted Oregon as the 33rd state while retaining control of Washington and Idaho as territories. These territories became states in 1889 and 1890, respectively. By then, hundreds of thousands of Americans had traveled west on the Oregon Trail to the northwest states that U.S. missionaries had played a significant role in settling.