The first European to explore the Canadian River was Juan de Oñate, the Spanish Governor of New Mexico, who followed the river from its origin to the western plains of what is now Oklahoma in 1601. Spanish traders and hunters were soon actively working in this area. French voyageurs were active along the lower Canadian. Bénard de la Harpe explored between the mouth of the river and the Kiamichi Mountains in 1715. Pierre and Paul Mallet followed the entire length of the river in 1740, as did another expedition led by Fabry de La Bruyere in 1741. The Louisiana Purchase in 1803 resulted in all of the land east of the New Mexico border being acquired by the United States.