Fort Starke
The fictional Fort Starke appears in She War a Yellow Ribbon, Rio Grande, The Command and stories by James Warner Bellah.
In She War a Yellow Ribbon Fort Starke seems to be located near the Kiowa reservation, & thus in Oklahoma or a neighboring territory or state - Arkansas, Texas, New Mexico, Colorado, Kansas, or Missouri.
The Fort Starke in Rio Grande might be an entirely different fort with the same name as the first one, founded in the years between the fictional dates of 1876 and 1879-80 of those movies.
In Rio Grande people come from Texas to Fort Starke from Texas, showing that Fort Starke is not in Texas. But people also cross the Rio Grande river into Mexico after travelling a few days from Fort Starke. Thus Fort Starke should be in the southeastern section of New Mexico, a few days ride south across the westernmost part of Texas to the Rio Grande and Mexico.
And that should be hundreds of miles from the Kiowa reservation and the other Fort Starke.
Here is a link to a discussion of the location of Fort Starke in the stories of James Warner Bellah and not in the movies.
https://websiteofahistoricalpolymath.wordpress.com/timelines/time-line-of-the-james-warner-bellahs-westerncavalry-stories/comment-page-1/?unapproved=1783&moderation-hash=4481ec1c3f1d820df62ae3faa91f9de7#comment-1783
"These stories are about an unidentified Cavalry regiment posted at Fort Starke. The location of Fort Stark is never exactly identified, although hints, often conflicting, are given. Also, the tribes that are mentioned and the locations further obscure the possibilities, which makes sense as these stories are really an encapsulation of the myth and legend of the Cavalry during the period of the Indian wars. That being said, most of the stories seem to be situated in the western Kansas/eastern Colorado area, although some stretch as far south as the Texas and across the Rio Grande, and Arizona."