This article examines early relations between the Illinois nations and French explorers, traders, and missionaries in the late seventeenth century. Following their encounter in the Pays des Illinois (Illinois Country), French newcomers came to believe that the Missouri River possessed an abundance of flora, fauna, fertile soil, and easily cut through the heart of North America to the Pacific Ocean. This was no accident. The Illinois deliberately withheld, emphasized, manipulated, and conveyed details concerning their western geography to French missionaries and fur traders, whose novel technologies, trade goods, and spiritual power they sought to secure for themselves. By articulating a carefully crafted "myth of the Missouri," the Illinois sought to direct French commerce and proselytization toward themselves and their allies up the Missouri River, like the Osage and Missouria, rather than to see French manet8a (other-than-human power) in the form of trade goods and Christian prayer fall into the hands of their enemies on the lower Mississippi. The Illinois strategy to attract French alliance, commerce, and spiritual power (manet8a) may have contributed to the century-long European and Euro-American belief in an expedient Missouri River route from the American Midwest to the Pacific Ocean. By arguing that the Illinois confederacy shaped European newcomers' understanding and perceptions of North America to further their own economic, political, and spiritual goals, this article contributes to the historiography regarding the role played by rumors, falsehoods, and fabrications in early colonial encounters as well as in the European and later Euro-American misunderstanding of the American Midwest's geography.