A few weeks ago, I was at the Kansas Preservation Conference in Dodge City and a tour took us to see where the Santa Fe Trail ruts ran down to the Arkansas River. One point, the Middle Crossing, marked a ford in the river where wagon teams could cross as they set out on the trail’s waterless and dangerous Cimarron Route to Santa Fe.
An often forgotten part of the story is this river crossing’s international legacy. The Adams-Onis Treaty of 1819 designated the Arkansas River west of the 100th Meridian as the northern boundary of New Spain. A few years later, it was the northern border of the Republic of Mexico. This meant that in the 1820s, 1830s, and early 1840s, teams on the Santa Fe Trail crossing the Arkansas at the Middle Crossing would have struggled up the south bank of the Arkansas into Mexico. The Arkansas was also Mexico’s border up to the Rocky Mountains.
After 1836, the Republic of Texas claimed lands up to the Arkansas as well, although Texas was unable to do much to back up that claim. The area was remote and sparsely populated with little infrastructure. Comanches, not customs agents, were the greater concern.
This border lasted until the Mexican American War of 1846 and in 1848, northern Mexico became the American Southwest. The Santa Fe Trail continued as a national rather than international route. Thereafter, both sides of the Middle Crossing lay in the boundaries of first Indian Territory, then Kansas Territory, and finally, the State of Kansas.