"...summer-long Red River Offensive that captured the Chickasaw Nation's capital at Tishomingo and placed American cavalry on the border with Texas at the Red River for the first time; additional infantry thrusts deeper into hillier, more remote Choctaw territory to clear out the most stubborn war bands ended with the first American push into northeast Texas with the capture of Texarkana on September 11th, and six days later American forces four hundred kilometers west raided across the Red River, capturing Wichita Falls for a period of ten days before withdrawing thanks to a counterattack by the Texas State Militia, though not before dynamiting the city's grain elevators and train depot and ripping up railroad tracks, leaving them tied around nearby trees. With the US Army having occupied Amarillo even further west in the Panhandle region for over a year and capturing Lubbock in early October with the focus on Los Pasos entirely satisfied, the defenses of northern and western Texas were essentially in tatters, a fact on the ground that was not lost on Native leadership.
It was in this context that the defeated leaders of the Six Tribes - the Five Nations along with the Osage - gathered at Kansas City on October 8th, 1915, to sign instruments of surrender to the "Great White Father," as American leadership was derisively known amongst Natives. Considering the bloody and cruel history of relations between white settlers and indigenous nations in North America, the Treaty of Kansas City was, by all accounts, fairly mild, though many Natives didn't particularly consider it that way. To the Cherokee in particular, Kansas City represented the final chapter in a century-long humiliation that began with the tensions in northeastern Georgia and evolved into the Trail of Tears of the 1830s. In hindsight, the terms imposed on the Five Nations could have been considerably worse.
The Indian Territory had been regarded as a protectorate of the Confederacy since 1863 and the Five Nations were permitted under treaties with Richmond to send non-voting delegates to advocate on their behalf in the Confederate Congress. That the Indian Territory had escaped being absorbed as a state by the Confederacy and the Natives within it put to the sword was, in some ways, a quirk of history - all Five Nations kept slaves themselves, and in elite Confederate circles this was taken as a sign that it was possible to "civilize" the indigenous peoples of the Americas, because keeping Negro slaves was to them after all the epitome and end stage of white civilization. Accordingly, though it was a minority and oft-unspoken view, there were a fair deal of Confederate leaders throughout the previous fifty years who considered the Five Nations more civilized and enlightened than the Yankees; the more common, indeed plurality, opinion was that the Natives were useful as a buffer and as allies and thus in good esteem.
To many Confederates, then, they were of the mind that the Five Nations should have allowed Richmond to negotiate on their behalf at the end of the war, but Natives had always viewed their relations with Richmond as bilateral, and now sought to approach Philadelphia the same way. It was a stroke of luck that the American delegation sent to Kansas City was inexperienced and that the United States was in the midst of secretly negotiating Mexico's exit from the war as well; unlike with Chile, the United States was in the mood to be more gracious than it would have been had the titanic victories of spring and summer 1915 not occurred.
The most straightforward demand of the United States was the transfer of protectorate status from Richmond to Philadelphia; American diplomats would represent Native interests with the rest of the world, and the Six Nations and the smaller tribes who leased their lands would make no bilateral agreements with any other nation independently of one another or without consultations with the United States. Beyond that, though, the "Indian Territory" would be regarded as the territory of "all the tribes residing within it" and not as an integral part of the United States. However, Americans would enjoy considerable extraterritorial rights; they could not be tried for crimes under tribal law, their property rights would be respected, and they would enjoy free movement and rights of residency within the Indian Territory. In practice, this meant that Americans could come to Native lands as often as they pleased and do essentially whatever they wanted, lending to the area's reputation for vice and violence in the decades to come.
Furthermore, lands in central, northwestern and southwestern Indian Country would be carved off as new "nations" for white and Black settlers, who would be on those lands permitted to write their own local laws which Natives would be governed by. With the exception of the Oklahoma Country in the central part of the state adjacent to the Choctaw, Seminole and Pottawotamie lands, these territories were generally harsher and less suitable for agriculture than other areas of territory, and freedmen who flocked to the possibility of a new life in the Indian Territory were often left with desolate, difficult land that performed poorly in good times, to say nothing of the severe droughts twenty years later during the Dust Bowl.
The United States was satisfied with leaving Indian Territory out of its borders, though, thanks to a unilaterally favorable minerals treaty. The Indian Territory would be permitted to export all agricultural, industrial and, crucially, raw resource products exclusively to the United States for a period of twenty years and would be beholden to importing finished and raw goods exclusively from the United States for a period of forty. This economic vassalization was intended to leverage American advantages in the Osage Hills oilfields, which some Congressmen of both parties had otherwise suggested simply annexing to Missouri or Kansas outright. In part, too, it reflected the lack of awareness that Philadelphia had in terms of just how much oil there was on Native land - it was generally thought that the Osage Hills would be exhausted as soon as 1940. Additionally, there was some partisan scuffle over exactly how far to go with the Indian Territory - Liberals generally assumed that due to its similar economic profile an Indian state would be quickly overrun with white settlers and soon vote lockstep Democrat like Missouri or Kansas, while Democrats assumed that due to Natives and Blacks generally favoring Liberal candidates historically, a future Indian state would simply add another two Liberal Senators. With both parties assuming that adding the Indian Territory to the United States would benefit the opposition, keeping it a supine vassal for the next half-century while sucking it dry seemed the better solution.
The chiefs of the various Native tribes begrudgingly signed this treaty on October 12th, still celebrated as Treaty Day in what is now the Confederated Nations of Sequoyah. The Indian Territory had exited the war with, all things considered, relatively low loss of life and, as it turned out, a remarkably favorable settlement on mineral rights, particularly for the Osage and Cherokee. The United States now had the perfect place from which to attack the industrial nodes of northern Texas directly, and one more domino had fallen for Philadelphia in terms of removing opponents from the board..."
- Bleeding Heartland: The Midlands Front of the Great American War [1]
[1] Once again, full confession that my thumb is pretty heavily on the scale here in keeping alt-Oklahoma out of the United States, but having an Indigenous Dubai/Kazakhstan in the middle of the continent is too interesting a hook to avoid even if, realistically, there's little chance that either the Liberal administration and Democratic Congress of the United States would ever be this magnanimous in dealing with the Five Nations. Mutual mistrust and, unspoken but surely considered, the potential for perpetual guerilla violence is my in-story excuse for making this happen.
