From The Comanche Empire, by Pekka Hämäläinen (Yale U. Press, 2008), pp. 152-154:
With the passing of the Indian Removal Act in 1830, the United States government began a wholesale relocation of eastern Indians across the Mississippi valley—the proclaimed permanent Indian frontier—into Indian Territory in what today are Oklahoma and Kansas. The removal policy brought thousands of Indians into present-day Oklahoma and Kansas, creating a new and deeply volatile geopolitical entity on Comanchería’s border. The most populous of the transplanted peoples—the Cherokees, Creeks, Chickasaws, and Choctaws—were placed in the southern and western sections of Indian Territory where, around the Wichita Mountains, their lands overlapped with Comanchería’s eastern fringe. Hundreds of removed Cherokees, Delawares, Shawnees, and Kickapoos also moved across the Red River into Texas, where Mexican officials offered them legal land grants if they served as border sentinels to protect the province from Comanche raiders and to keep illegal American traders from entering Comanchería.
A clash was immediate and, it seems, inevitable. Dismayed by the agricultural prospects in subhumid Oklahoma, many immigrant groups began to experiment with bison hunting. The westernmost bands of the Delawares, Kickapoos, and Shawnees developed a typical prairie economy of farming and foraging and started making regular hunting excursions to the plains, tapping into Comanchería’s bison reserves. Comanches responded to these transgressions by attacking the intruders and by raiding deep into Indian Territory to exact revenge and to plunder maize, cattle, and captives. The death toll climbed on both sides. The fighting also disrupted the Comanche-American trade that had flourished for two decades on the southern plains….
In moving across the Mississippi valley, the immigrant nations had encroached upon the Comanche realm but, more important, they had entered an ancient borderland where commercial gravity tended to pull peoples together. Their position between the livestock-rich Comanchería and the livestock-hungry Missouri and Arkansas territories invited the removed Indians to become middlemen who facilitated the movement of goods among the centers of wealth around them. Like the Wichitas, French, and Americans before them, several of the immigrant nations responded. A propitious diplomatic opportunity to attach themselves to the Comanche trade network opened to them in 1834 and 1835 when the U.S. government sponsored two large-scale political meetings among the Comanches, their allies, and the immigrant Indians, hoping to quell the violence that threatened to abort the entire Indian removal policy. In August 1835, some seven thousand Comanches and their Wichita allies gathered at Camp Holmes near the Canadian River, where nineteen Comanche chiefs signed a treaty and agreed to open their lands “west of the Cross Timber” to the immigrant tribes. In return, they expected trade.
The immigrant tribes did not disappoint, and within a few years the border region between Comanchería and Indian Territory had become a site for thriving trade. Although uprooted and dislodged, the removed Indians could still generate impressive surpluses of manufactured and agricultural products, which they were keen to exchange for the plains products they needed to survive in their new homelands. Comanches sponsored massive intertribal gatherings along the Red and Brazos rivers and on the salt plains of north-central Oklahoma, often sending messengers to Indian Territory to announce a forthcoming fair. Cherokee, Choctaw, Chickasaw, Creek, and Seminole trading convoys frequented Comanche rancherías, bringing in maize, wheat, potatoes, tobacco, vermilion, wampum, beads, powder, lead, and government-issued rifles. In exchange, they received robes, skins, meat, salt, horses, and mules, a part of which they traded again to American settlers in Missouri, Arkansas, and Louisiana. Sometimes the seminomadic and more mobile Delawares, Kickapoos, and Shawnees served as intermediaries, moving commodities between Indian Territory and Comanchería. The thriving commerce also pulled more marginal groups into the Comanche orbit….
The dynamics of this exchange mirrored the direct Comanche-American trade it had supplanted, but there was an important new element: slave trade. The removed Cherokees, Choctaws, Chickasaws, Creeks, and Seminoles [the “Five Civilized Tribes“] had brought with them approximately five thousand black slaves, and the bondage institution persisted in Indian Territory as the planter-shareholder elite set out to rebuild its exchange-oriented cotton and tobacco economy. This created secure markets for Comanche slavers who now commanded extensive raiding domains in Texas and northern Mexico. More improvised than organized, the slave traffic offered multiple opportunities for its practitioners. Removed Indians purchased kidnapped Mexicans, Anglo-Americans, and black slaves from Comanches, either to augment their own labor force or to resell them to American Indian agents, who generally ransomed the offered captives, especially if they had fair skin. At times Comanches bypassed the middlemen and took their captives directly to U.S. officials at Fort Gibson and other frontier posts, and sometimes they relied on comanchero intermediaries who then delivered the captives to American agents. Occasionally, Comanches even kidnapped black slaves from Cherokees, Chickasaws, Choctaws, and Creeks and then sold them to Delawares, Kickapoos, and Shawnees. They also captured black runaway slaves from Indian Territory and incorporated them into their ranks.