Originally named Misión San Antonio de Valero, the Alamo served as home to missionaries and their Indian converts for nearly seventy years. Construction began on the present site in 1724. In 1793, Spanish officials secularized San Antonio's five missions and distributed their lands to the remaining Indian residents. These men and women continued to farm the fields, once the mission's but now their own, and participated in the growing community of San Antonio.

In the early 1800s, the Spanish military stationed a cavalry unit at the former mission. The soldiers referred to the old mission as the Alamo (the Spanish word for "cottonwood") in honor of their hometown Alamo de Parras, Coahuila. The post's commander established the first recorded hospital in Texas in the Long Barrack. The Alamo was home to both Revolutionaries and Royalists during Mexico's ten-year struggle for independence. The military — Spanish, Rebel, and then Mexican — continued to occupy the Alamo until the Texas Revolution.

San Antonio and the Alamo played a critical role in the Texas Revolution. In December 1835, Ben Milam led Texian and Tejano volunteers against Mexican troops quartered in the city. After five days of house-to-house fighting, they forced General Martín Perfecto de Cós and his soldiers to surrender. The victorious volunteers then occupied the Alamo — already fortified prior to the battle by Cós' men — and strengthened its defenses.

On February 23, 1836, the arrival of General Antonio López de Santa Anna's army outside San Antonio nearly caught them by surprise. Undaunted, the Texians and Tejanos prepared to defend the Alamo together. The defenders held out for 13 days against Santa Anna's army. William B. Travis, the commander of the Alamo sent forth couriers carrying pleas for help to communities in Texas. On the eighth day of the siege, a band of 32 volunteers from Gonzales arrived, bringing the number of defenders to nearly two hundred. Legend holds that with the possibility of additional help fading, Colonel Travis drew a line on the ground and asked any man willing to stay and fight to step over — all except one did. As the defenders saw it, the Alamo was the key to the defense of Texas, and they were ready to give their lives rather than surrender their position to General Santa Anna. Among the Alamo's garrison were Jim Bowie, renowned knife fighter, and David Crockett, famed frontiersman and former congressman from Tennessee.

The final assault came before daybreak on the morning of March 6, 1836, as columns of Mexican soldiers emerged from the predawn darkness and headed for the Alamo's walls. Cannon and small arms fire from inside the Alamo beat back several attacks. Regrouping, the Mexicans scaled the walls and rushed into the compound. Once inside, they turned a captured cannon on the Long Barrack and church, blasting open the barricaded doors. The desperate struggle continued until the defenders were overwhelmed. By sunrise, the battle had ended and Santa Anna entered the Alamo compound to survey the scene of his victory.

While the facts surrounding the siege of the Alamo continue to be debated, there is no doubt about what the battle has come to symbolize. People worldwide continue to remember the Alamo as a heroic struggle against impossible odds — a place where men made the ultimate sacrifice for freedom. For this reason, the Alamo remains hallowed ground and the Shrine of Texas Liberty.