As the beaver trade waned in the 1830s, so did economic reasons for an American toehold in the Oregon country, still under joint British-American occupancy. Religion shifted the balance of power, however, when American Protestant missionaries crossed the Rocky Mountains with an eye toward converting the tribes of the Northwest. Soon these men brought their wives with them as well. In 1836, Narcissa Whitman and Eliza Spalding were the first Euro-American women to cross South Pass, and these people became the vanguard of American settlement of Oregon.