Castroville is a city in Medina County, Texas, United States. The population was 2,680 at the 2010 census. Prior to 1893, Castroville was the first county seat of Medina County. Castroville is known for its influential Alsatian-Texan architecture, people, and culture. Most Alsatians that came to Castroville spoke Alsatian. To say Castroville's ancestral influences are broadly French would not be true, as they are more strictly Alsatian, a culture and language still kept alive by its residents.