It's 1845, and the status of the Republic of Texas is very much in flux. Mexico still wants it back, and within both Texas and the United States there is a lot of wrangling as to its future. Expansionists such as ex-President Andrew Jackson want to bring Texas into the Union, while some in the United States are resisting adding a slave state and some in Texas prefer independence.
Andrew Jackson, who seems to be heading the pro-annexation campaign — President John Tyler must have been taking a nap — receives some disturbing news. Reports from Texas are that Sam Houston, former president of the republic and still the most influential man there, has come out against annexation.Jackson commissions one Devereaux Burke (Gable), Texas cattleman, to head back home in hopes of contacting Houston and getting him to change his opinion, which will likely be decisive.
Burke makes it to Austin, where he meets anti-annexation leader Tom Craden (Crawford) and Craden's girlfriend Martha Ronda (Gardner), who runs the local paper. Both Tom and Martha are very much against Texas joining the United States, Martha because she fears war with Mexico, and Craden because he wants to be president of Texas. Martha starts to develop feelings for Burke which complicate her political loyalties. Tom for his part is willing to go to some extreme, violent ends to stop annexation.
- Artistic License: After the opening title card gives the date as 1845, the movie cuts to a scene where Andrew Jackson and some Democratic bigwigs are worrying about the wisdom of running James Polk on a pro-annexation platform. Polk was elected president in November 1844. Plus, the movie never answers why the point man for the annexation movement is Jackson rather than John Tyler, who was president at the time.note
- The Cavalry: An extremely rare example of an American Western where the Indians are the cavalry. Craden and his men are still assaulting the legislature when arrows start thudding into the walls. It's Sam Houston, at the head of the tribe of Apache he's been negotiating with, returning to Austin to put a stop to Craden's rebellion. Just like that, the battle is over and the good guys win.
- Chekhov's Gun: Burke winds up floating down the Pecos River as he tries to escape Craden and Craden's goon squad. This pays off a bit later when Craden shows up in Austin to present Sam Houston's pro-annexation letter, only to find the letter soaked and illegible for having been in the water.
- Divided States of America: Craden presents his master plan to Burke, the reluctant state senators, and Martha. He believes that he can get Mexico to cede California and the Southwest to Texas. Then when civil war that Craden (correctly) anticipates will happen between the free and slave states, Craden thinks the slave states will join their sister slave state Texas. He presents his audience with a map that shows a Greater Texas occupying about 3/4 of the modern-day USA, with a rump United States occupying the northwest corner. Everyone in his audience is appalled.
- Dramatic Thunder: A clap of thunder is heard during the tense meeting between Sam Houston, Craden, and Burke, and further thunder and lightning is heard during the chase scene where Craden and his men come after Burke. Battle in the Rain is averted because it doesn't actually start raining until after Burke has won, killing all the bad guys but Craven.
- Easily Forgiven: Craden attempted to kill Burke. He kidnapped three pro-annexation senators. Then he launched a treasonous armed assault against the Texas legislature that gets a lot of people killed. What happens to him? After he loses a fistfight to Burke, he's forgiven, and he even gets to hold the flag in the army of Texas preparing to fight Mexico.
- Historical Domain Character: Andrew Jackson, Sam Houston, and the last President of Texas, Anson Jones.
- Injun Country: Craden and Burke's platonic Meet Cute comes when Burke saves Craden from some murderous Apache. Surprisingly averted later, when the rest of the Apache turn out to be not just peaceful, but actively on the side of Houston.
- Instantly Proven Wrong: Two of Martha's cooks are arguing loudly in Spanish. Martha tells them, in Spanish, to knock it off. As she and Burke leave she says "They'll be quiet." Instantly the two cooks start screaming at each other again.
- Love Triangle: Burke, Craden, and the lovely Martha. No prizes guessing who will win the love triangle, since one of the men is Clark Gable and the other isn't.
- No Peripheral Vision: Burke gets the jump on Craden's goon squad when they ride down a trail and fail to see him in the tree brances directly over their heads. Of course, it was dark.
- Romantic False Lead: In this film Tom Craden is the "Guy who will lose the girl to Clark Gable" character.
- Tempting Fate: Burke's sidekick Luther is wounded by a shot in the arm early in the film and is put out of fighting action. At the climactic siege of the legislature, Luther gets up on the rampart and says "So glad we're shootin'! I'm back in shape again!" He's immediately shot in the arm once again.
- Young Future Famous People: Burke is led from the Apache camp back to the way to Austin by a teenaged boy named Geronimo. Geronimo confidently asserts that he'll be chief one day.