"Oklahoma Territory" was created on 5 May 1890 and was added to from time to time after each subsequent land opening (whether by "run" or by lottery).

The "Indian Nations", "The Territories", or "The Nations", are all informal means of referring to the area now known, principally, as eastern Oklahoma. This was especially true of the northeastern area (occupied by the Cherokee Nation, and the reservations of the Deleware, Kickapoo, Miami, Ottawa, Peoria, Quapaw, and Seneca). "Indian Territory" generally refers to what is now all of Oklahoma excepting the panhandle which was "No Man's Land" (or "Cimarron Territory") until it was added to Oklahoma Territory by Act of Congress in 1890; and it didn't include "Greer County, Texas" which was created when the army mistook the north fork of the Red River as the main channel; (Greer county became part of Oklahoma Territory after the Supreme Court ruled against Texas in 1898 and established the boundary as the right bank of the [true] Red River).