During the Middle Ages, the most prominent dynasties in the area were the Villota and Entrambasaguas families, which fought for the control of administrative and political positions. The conflict between these two families dates back to the 15th century, when they litigated about the ownership of the local foundries. In the second half of the 18th century, their disagreements brought them all the way to the Royal Chancery of Valladolid. Guriezo was quite active in the iron trade with Biscay's foundries during the late Middle Ages. Guriezo played a role in the development of the prosperous Basque iron industry; in 1846, members of the prominent Ybarra family acquired the factory of La Merced, which operated until 1854.