Joint Base San Antonio was created out of an Army fort and several Air Force installations. The oldest of these was Fort Sam Houston, originally established in Alamo City as a Quartermaster Depot in 1845. The post later relocated to a parcel of land donated by the citizens of San Antonio in 1876, and became a permanent military installation fourteen years later.


The Apache war chief Geronimo was imprisoned at the Sam Houston Quadrangle, on what is now JBSA grounds, for about six weeks in 1886, before being transferred to various Army posts around the West.


From 1910 until World War II, Sam Houston was the largest Army post in the United States, and was the training grounds to many outstanding American soldiers, including Dwight D. Eisenhower, who was stationed here at the start of World War II.


At the end of World War II, the decision was finalized to make this post the main Army medical training facility. In the years following, the Brooke General Hospital was built, and the Institute of Surgical Research, the Burn Center, the Medical Field Service School, and Health Services Command were established.


The 2005 Base Realignment and Closure Commission cemented Fort Sam Houston as the "Home of the Military Medicine" via the consolidation of all military medical training. The post is today the largest and most significant military medical training facility on earth.