The so-called Duke of Cantabria (possibly Cantabria had been a duchy in the Visigothic Kingdom) married the heiress of the recently formed Kingdom of Asturias in 739, so that the Kingdom extended along much of the northern coast of Spain as a result of the marriage.
When the sons of Alfonso VII divided his Kingdom in 1157, the elder, whose share was Castile, took part of the former Kingdom of Leon, including Cantabria or Asturias de Santillana, which as a result became the coastal region of Old Castile.
In 1833 it became the province of Santander.
In post-Franco Spain the province became the community of Cantabria, whose first parliament was elected in 1983 and whose executive is called the Diputación. Of the other 16 Communities only La Rioja and the Balearic Islands are smaller in area and only Navarre (narrowly) and La Rioja have fewer people.