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 (32 km) west of San Antonio.

They were taken by ship to Lavaca Bay and traveled 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, but for generations, the residents remained insular.

The descendants of the original settlers worked diligently to preserve their language, whose usage in Europe has been diminished by the political actions of France and Germany, especially since World War II.

The Steinbach Haus (originally built between 1618 and 1648 in Wahlbach, Alsace) was dismantled and reconstructed in Castroville in 1998.

According to the United States Census Bureau, the city has a total area of 2.5 square miles (6.5 km2), of which 0.39% is covered with water.