Factual error: Approximately 2 hours and 10 minutes into the "restored" full-length video version, there's a birthday party for little Lisa Dickinson, and the Alamo defenders sing "Happy Birthday" to her. The Alamo battle happened in 1836. According to David Ewen's "All the Years of American Popular Music," the song "Happy Birthday to You" was composed and copyrighted by sisters Patty and Mildred J. Hill, first as "Good Morning to All," in 1893.
Factual error: The movie's opening scene manages to get wrong almost every historical detail except the names. Sam Houston was never in San Antonio with Colonels Neill, Travis, and Bowie. Then-governor Henry Smith - not General Houston - made Travis a colonel (in December). Bowie did a lot of drinking and carousing, but that never caused him to be demoted or to lose a command. Bowie did marry into the Mexican aristocracy, and he acquired a lot of land, but it would have been ridiculous for Travis to therefore doubt his loyalty to the rebellion. Bowie was one of the rebellion's best-known firebrands and had just taken San Antonio from the Mexicans.
Factual error: The mock-up of San Antonio de Bexar shows the buildings connected mostly along a single street, like towns in innumerable westerns. Actually, San Antonio was laid out with its buildings around plazas, in the Spanish style.
Factual error: When Bowie first walks into the chapel, you can see all the way back to the eastern wall. By this time, there would have been a dirt ramp leading up to two 12-pound cannon that overlooked the wall. In the same scene, the doorway to Bowie's left is where the powder magazine would have been, and to the right is where the women and children were. In the movie, these uses for the rooms are reversed.
Factual error: Travis says he is married. Actually he was divorced by this time.
Factual error: When the scout comes in and describes a huge cannon the Mexicans have, there are actually two mistakes, one of continuity and one historical. The continuity mistake involves the powder horn the scout is wearing. When you first see him it is facing with the tip one direction. The scene then cuts to Bowie. When it cuts back to the scout again the powder horn is turned the opposite direction. The historical mistake involves the cannon itself. The largest cannon used in the battle was in possession of the Alamo defenders. Santa Anna brought only small field pieces on the winter march from Mexico. (00:30:00)
Factual error: The final assault began before dawn, around 5:00 in the morning. Travis was killed almost immediately by a shot in the head.
Factual error: Bowie's wife had died in 1833, and from cholera, not plague. Her two sisters actually joined Bowie in the Alamo.
Factual error: When Crockett and Bowie discover Sande's powder and weapons cache, Davy picks one up and exclaims, "Rifles!" In fact, those are smoothbore military muskets, possibly British pattern, French pattern, Spanish Model 1807, or Springfield Model 1822, and only the British army had rifle regiments. Davy, being a rifleman would never mistake a musket for a rifle.
Factual error: Travis never took his orders from Houston, and Bowie never took his orders from Travis. Colonel Neill (not Houston) left Travis in charge at San Antonio while he went on a 20-day furlough to be with his family - not to go north with Houston (since Houston wasn't there to begin with). Travis then rashly asked the militia to elect a leader, and they chose Bowie. Eventually the two agreed to share command, Travis over the regulars and the volunteer cavalry, Bowie over the garrison volunteers. By February 24th, however, Bowie was very ill (probably with typhoid) and was bedridden for the rest of the siege, leaving Travis as the de facto commander. In the movie, he isn't confined to his bed until the final assault, and then as the result of a wound.
Factual error: The facade of the chapel is slightly anachronistic: the two upper windows were not added until the 1840's, and the top was more level - for the movie, it was deliberately distorted to suggest the famous hump by which people recognize the Alamo today. The chapel itself was built to scale, but the rest of the compound is about 75% as big as the original - otherwise, the Alamo compound is generally quite accurate.
Factual error: Sam Houston twice places San Antonio on the Rio Grande (once he calls it the "Rio Bravo," which is the Mexican name for the same river). But San Antonio is on the San Antonio River, about 150 miles from the Rio Grande. Travis likewise seems to have a shaky grasp of geography. When he is explaining the situation to Crockett, he makes an "X" in the dirt and says that that's Santa Anna. Then he makes a line to represent the Sabine River. On the opposite side of the line, he makes another "X," to represent Houston. Then he jabs his sword into the dirt and says, "Somewhere in between . . . is the Alamo." His little map puts both Houston and the Alamo somewhere in Louisiana.
Factual error: Houston sent Bowie to San Antonio with orders to blow up the Alamo and withdraw to Gonzales. It was Bowie's idea (not Travis's) to stay and fortify the Alamo.
Factual error: Colonel Fannin's men were massacred after the siege of the Alamo, not before. The most likely reason Fannin never got to the Alamo with reinforcements was simply that he didn't have any supply wagons
Factual error: Travis calls Susannah Dickinson his "cousin." They were not related. And Susannah would have been about 15 years old, with black hair, while her daughter, Angelina, was about 15 months.