Castroville was established in 1844 by Henri Castro, an empresario of the Republic of Texas, who brought several dozen European families to the area from Alsace and adjoining Baden to populate his land grant along the Medina River 20 miles west of San Antonio. The first colonists disembarked at Galveston on January 9, 1843. They were taken by ship to Lavaca Bay and travelled overland to San Antonio, where they took shelter in abandoned buildings until the Texas Rangers were prepared to escort them to their land and protect them from hostile Indians. On September 2, 1844, the first colonists arrived at Castro's land grant on the Medina River.
After a few hard years, the town and surrounding farms flourished, although for generations, the residents remained insular. In Castroville's first century, a visitor would be more likely to hear Alsatian — a language spoken in Europe before high German was invented— than English spoken in the town's homes, stores and taverns. Modern Alsatian travelers have noted that the dialect spoken in Castroville is more like that spoken in the 1840s. The descendants of the original settlers have diligently worked to preserve their language, which is being slowly eradicated by political actions between France and Germany, especially since WWII.
Today, though, native speakers of Alsatian are dying out, and fewer of the town's residents can trace their ancestry back to the original Castro colonists. The suburbs of nearby San Antonio are encroaching, and much of the town has been made a national historic district to preserve the unique, sloped-roof architecture of dozens of original Alsatian homes and shops.
Castroville is a sister city of Ensisheim (Alsace) in France.