Their areas and populations are as follows: Its history starts in prehistoric times, evidences of whom can be found at the caves of Puente Viesgo, La Garma (Omoño), Santoña and Miera.

King Alfonso I of Asturias (739-757), Duke of Cantabria, ordered the resettlement of what now is known as the comarca of Trasmiera, where there was little presence of human settlements.

The capital of the merindad was in Hoz de Anero where the Assemblies of Cudeyo, Ribamontán, Siete Villas, Cesto and Voto took place.

It is known that at the beginning of the 12th century a large number of masons of Trasmiera were called to work in the construction of Avila's City Walls.

The job was transmitted from fathers to sons, so they enjoyed an especial learning that allowed them to be Masters, and thus to direct cathedral constructions before the thirties.

Another one of the traditional jobs of Cantabria and above all of the comarca of Trasmiera is the altarpiece-making; to conceive and compose an altarpiece, to come up with and arrange its design.

After the rules of the Council of Trent in 1563, which promoted the cult to icons and altarpieces, many workshops arose in this Cantabrian comarca.

Many of these altarpiece-makers were consummate architects and had fine workshops where carvers, carpenters, sculptors, gilders and a whole series of necessary jobs for their work's culmination.

The comarca of Trasmiera was a cradle for prestigious bellfounders, whose fame transcended the Spanish borders, which granted them works in some part of Europe and America.

They reached such significance that many specialists remark that there is no cathedral, basilica or church that hasn't had in its belfries some work of a Cantabrian bellmaker.

In 1753, the bell considered the largest of Spain, weighing 22 tonnes, was made by master founders of Arnuero destined to the cathedral of Toledo, and whose making took two years.

Some chronicles tell that when the bell was used for the first time, it broke all the glasses of the city and caused all the pregnant ladies to miscarry, which forced its makers to make holes in it to lower its ringing.

In 2004, as a wedding present to the Princes of Asturias, Cantabria gave them the "Virgen Bien Aparecida" bell,[8] which weighs 1,600 kg and was founded in Gajano (Marina de Cudeyo) by two of the last master bellmakers and heirs to the Trasmeran tradition, the Portilla brothers.