On the hillside, the wagon ruts of the Santa Fe Trail bear witness to time and to nations moving east and west. When Mexico won its independence from Spain in 1821, legal trade began between the United States and Mexico. The end of the U.S.-Mexican War in 1848 expanded the interests and obligations of the United States. As Native Americans and Mexicans defended themselves against the invasion of their homeland, concerns for safety increased among settlers, traders, merchants, travelers, townspeople, and farmers. To protect its new U.S. territory and extend its influence and security to travelers on the trail and to newly arriving American settlers, the United States established Fort Union in 1851, and orders directed Major Carleton's Company K 1st Dragoons to remain in motion that summer and fall along the Cimarron route to protect travel and commerce between the Missouri frontier and the territory.