Connected to the birth of Castile, the Merindades, standing for the northernmost comarca of the province of Burgos, was part of the creation of the administrative division by King Peter.
Many of its towns were once under Islamic rule, with Muslim and Mudéjar populations persisting long after the Reconquista, particularly in the capital, where Arabic influences remain in toponymy and vocabulary.
The 1366 census lists Tudela first, followed by Tafalla, Artajona, Caparroso, Rada, Mélida, Carcastillo, Marcilla, Villafranca, Cadreita, Valtierra, Arguedas, Murillo, Cabanillas, Fustiñana, Cortes, Buñuel, Ribaforada, Fontellas, Ablitas, Monteagudo, Cascante, Pedriz, Tulebras, Murchante, Centreniego, Corella, and Castellón.
It also records governors (alcaides) in Monteagudo, Ablitas, Tafalla, Corella, Cortes, Sanchabarca, Peñaflor, Peña Redondo, and Valtierra.
Additionally, the census classified social groups, listing farmers, free citizens (francos), Moors, Jews, and fijosdalgo (hidalgos, nobles), who resided in Tudela, Cascante, Monteagudo, Arguedas, Fontellas, Cadreita, Valtierra, Marcilla, Caparroso, and other towns.