Adelantado mayor of Castile

Lamingueiro Fernández stated that since the 10th and 11th centuries, the Leonese monarchs tried to make their presence effective throughout their jurisdiction, for which reason they created the greater and lesser merinos, the tenants-in-chief, the alfoces and later, in the mid-13th-century reign of Alfonso X of Castile, the adelantados, in order to enforce their policies.

[1] By the reign of Ferdinand III of Castile the jurisdictions of the greater and lesser merinos were already fully defined.

[1] It was also Ferdinand III who appointed greater merinos for the Kingdom of Castile and later for those of León, Galicia, and Murcia.

[1] After the death of Ferdinand III, his son and heir Alfonso X maintained the same administrative divisions that had existed during his father's reign and thus, all his territories continued to be divided into four major merindades.

The heritability of the office caused it to become a more honorary rather than effective title, and from then on the greater adelantados gained more importance.