The Alamo was the name of a fortified Spanish mission located in San Antonio in the North American region of Texas on Earth. In 1836 it was the site of Battle of the Alamo.
In 2375, Miles O'Brien built a scale model of the mission. (DS9: "The Changing Face of Evil")
O'Brien and Bashir talked about visiting the real Alamo when O'Brien and his family left Deep Space 9 for Earth in late 2375. (DS9: "What You Leave Behind")