With the forced abdication of Alfonso III by his sons in 910, the Kingdom of Asturias split into three separate kingdoms of León, Galicia and Asturias. The three kingdoms were eventually reunited in 924 (León and Galicia in 914, Asturias later) under the crown of León. It continued under that name until incorporated into the Kingdom of Castile in 1230, after Ferdinand III became joint king of the two kingdoms. Nice to mention as well that by that time part of Asturias became Portugal so it didn't got incorporated to the Kingdom of Castile. The Portuguese borders today are the same as in 1230.