The Armstrong Roll was created after the Treaty of Dancing Rabbit Creek. There is a lengthy treaty and supplement. Reading the entire treaty and supplement will provide you with a better understanding of this roll.
Where they lived:
Treaty of Dancing Rabbit Creek–Article II. The United States under a grant specially to be made by the President of the U.S. shall cause to be conveyed to the Choctaw Nation a tract of country west of the Mississippi River, in fee simple to them and their descendants, to inure to them while they shall exist as a nation and live on it, beginning near Fort Smith where the Arkansas boundary crosses the Arkansas River, running thence to the source of the Canadian fork; if in the limits of the United States, or to those limits; thence due south to Red River, and down Red River to the west boundary of the Territory of Arkansas; thence north along that line to the beginning. The boundary of the same to be agreeably to the Treaty made and concluded at Washington City in the year 1825. The grant to be executed so soon as the present Treaty shall be ratified.
Treaty of 1825–Article I. The Choctaw Nation do hereby cede to the United States all that portion of the land ceded to them by the second article of the Treaty of Doak Stand, as aforesaid, lying east of a line beginning on the Arkansas, one hundred paces east of Fort Smith, and running thence, due south, to Red river: it being understood that this line shall constitute, and remain, the permanent boundary between the United States and the Choctaws; and the United States agreeing to remove such citizens as may be settled on the west side, to the east side of said line, and prevent future settlements from being made on the west thereof.
Treaty of Doak Stand–Article II. For and in consideration of the foregoing cession, on the part of the Choctaw nation, and in part satisfaction for the same, the Commissioners of the United States, in behalf of said States, do hereby cede to said nation, a tract of country west of the Mississippi River, situate between the Arkansas and Red River, and bounded as follows:– Beginning on the Arkansas River, where the lower boundary line of the Cherokees strikes the same; thence up the Arkansas to the Canadian Fork, and up the same to its source; thence due South to the Red River; thence down Red River, three miles below the mouth of Little River, which empties itself into Red River on the north side; thence a direct line to the beginning.
Choctaws wishing to become citizens of United States
Treaty of Dancing Rabbit Creek–Article XIV. Each Choctaw head of a family being desirous to remain and become a citizen of the States, shall be permitted to do so, by signifying his intention to the Agent within six months from the ratification of this Treaty, and he or she shall thereupon be entitled to a reservation1 of one section of six hundred and forty acres of land, to be bounded by sectional lines of survey; in like manner shall be entitled to one half that quantity for each unmarried child which is living with him over ten years of age; and a quarter section to such child as may be under 10 years of age, to adjoin the location of the parent. If they reside upon said lands intending to become citizens of the States for five years after the ratification of this Treaty, in that case a grant in fee simple shall issue; said reservation shall include the present improvement of the head of the family, or a portion of it. Persons who claim under this article shall not lose the privilege of a Choctaw citizen, but if they ever remove are not to be entitled to any portion of the Choctaw annuity.
Reservation, 640 acres. Not a Indian Reservation as we have today. ↩