Alfonso X was the king of Castile, León and Galicia from 1252 until his death. He established the form of modern Castilian Spanish.
Alfonso X was born Nov. 23, 1221, in Burgos, Castile. He was King of Castile and León from 1252–84. He claimed the title of Holy Roman emperor, but Gregory X persuaded him to renounce the claim. His second son succeded him as Sancho IV. Alfonso's court was a center of culture, producing the law code, the Siete Partidas, and establishing the form of modern Castilian Spanish. He died in 1284.