The Alamo is a former Spanish mission located in downtown San Antonio, Texas, and was an abandoned ruin when it was used as a fortification in 1836 by colonists against the harsh rule of dictator Antonio Lopez de Santa Anna; the resulting seige and massacre of the 189 men within led to Santa Anna's defeat at San Jacinto a short time later and the creation of the independent Republic of Texas.
Misión San Antonio de Valero was one of five missions constructed in the region that was later to become San Antonio de Bexar; the Valero mission's foundation was laid in 1724, and served the area for some seventy years. About 1793 the missions and the land they were on were divided and given over to the control of the Indian inhabitants, who continued to be productive farmers in the small San Antonio community while the mission buildings lay abandoned.
The Valero mission was inhabited again in the early-1800's, this time by a contingent of cavalry soldiers from the Coahuila town of Alamo de Parras, who gave the old ruins its present name from the familiar cottonwood trees which had grown about the site. The commander of the unit would build and establish the first hospital in Texas in what is called the Long Barrack, a structure built in front of and to the north of the main church building. The West Wall and South Barrack structures would be built prior to 1830, as the Alamo site grew into a fortification which served the military units of Spain and Mexico.
In the early 1820’s Americans began arriving in Tejas – the territory of Mexico north of the Rio Grande river – for the purpose of colonization. Sparsely-populated and un-productive at the time, the colonists soon turned the territory into Mexico’s most prosperous, with the additional benefit of strengthening Mexico’s claim to the area. Under the auspices of the constitution of 1824, the Texians (as the colonists called themselves) had the promise of having the territory admitted to Mexico as a state. Up until 1830 there was mutual respect between the central government and the colonists under Stephen F. Austin, who had made yearly trips to Mexico City as an act of fealty and to update the government on their progress. The relationship soured somewhat beginning in 1830, when Mexico's president Anastasio Bustamante became increasingly hostile towards the colonists, enacting higher taxes and duties, restricting shipping on the coast, and cancelling land contracts. In 1832 Butamante was overthrown in a coup led by Santa Anna, and for a short period the colonists enjoyed a respite, which ended when Austin again made a trip to Mexico City and was promply thrown into jail for daring to petition the government to admit Texas as a state under the 1824 constitution; he would remain there for eighteen months, and be released in the summer of 1835.
During his absence unrest continued to grow within the Tejas areas settled by the colonists, directed against the increasingly harsh rule of Santa Anna, now recognized as a dictatorship as he consolidated his power following the coup. Several settlements were occupied by Mexican regulars; the town of Bexar (San Antonio) was taken by General Marín Perfecto de Cós in the fall of 1835; and Lt. Francisco Castaneda with one hundred men was sent to the town of Gonzales to remove a cannon given to the settlers as a protection against Indian attacks. Not all went as planned: Castenada not only met stiff resistance from the settlers, but had to do so while looking at a white flag with the derisive words "Come and take it" printed on it. 
In December 1835, a force of Texians, Tejanos, and other volunteers under Ben Milam took Bexar after five days of fighting and compelled the surrender of Cós. The Alamo, strengthened considerably, was then occupied as a fortress.
Only fourteen people survived the siege and final assault.
- Susanna Dickinson, wife of Capt. Almeron Dickinson;
- Angelina Dickinson, their 15-month old daughter;
- Joe, Travis' slave;
- Gertrudis Navarro;
- Juana Navarro Alsbury;
- Alijo Perez;
- Ana Esparza, (wife of Gregorio Esparza), and their four children:
- Maria de Jesus Castro;
- Trinidad Saucedo;
- Petra Gonzales;
- Brigido Guerrero, a deserter from the Mexican Army who talked his way out of being killed by claiming to be a POW.
The Mexican forces lost more than 1,500 men. The massacre at the Alamo was memorialized in the cry, "Remember the Alamo!" and helped to galvanize resistance to Santa Anna and led to Texan independence.
The Texas Declaration of Independence declared:
- General Antonio Lopez Santa Ana ... having overturned the constitution of his country, now offers, as the cruel alternative, either abandon our homes ... or submit to the most intolerable of all tyranny ... He denies us the right of worshiping the Almighty according to the dictates of our own conscience.
Alamo Mission in San Antonio.
- The Encyclopedia of Military History, Dupuy & Dupuy, 1979