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.
Continuity mistake: In an early scene Travis and Dickenson are in Travis's office. Travis goes to the mantel, gets a cigar and pours himself a glass of sherry. In a later scene, when Travis meets Crockett in the cantina he refuses a drink from Crockett claiming he doesn't drink, ever.
Character mistake: In a conference with Crockett and Bowie, Travis states that Fannin in Goliad is preparing to relieve the Alamo and will be ready to "march south by the end of the week." Goliad is 90 miles south of San Antonio. To relieve the Alamo, Fannin would need to march north.
Revealing mistake: When Crockett, Bowie and their men are about to destroy the giant cannon, several of the men are standing right next to it at the moment one of them tosses the torch on the touch hole. Then, there's a big flash at the touchhole. In the very next shot, right before the cannon explodes, we see the cannon, but everyone has disappeared. There was no time for them to flee completely out of sight.
Other mistake: When Bowie and his men first enter the Alamo, Travis calls for the colors ceremony and the detail marches to the flagpole. One section is ordered to "halt", then the order "about face" is given. However, the detail does a "right face" instead.
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: 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: 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.
Plot hole: At the start of the final battle, the Mexican artillery is lined up wheel to wheel, and fires the opening salvo. Apparently Newton's third law doesn't apply in Texas, because none of the cannon recoil after firing.
Plot hole: The morning of the final battle, the sun rises behind the mission, silhouetting a sentry. When the ending credits roll, the sun sets behind the mission.
Continuity mistake: When Crockett's party first see San Antonio, they are carrying little more than blanket rolls on their horses - and no pack mules. However, when Crockett tells them to change into their best duds, top hats and other clothes appear from nowhere.
Continuity mistake: In the scene on the last assault on the Alamo, Mexican cavalry (in red coats) jump the palisade next to the chapel and are killed by a volley of musketry and their bodies are littered everywhere. Next time you see the area, however, the bodies have disappeared.