Diego Hurtado de Mendoza, 1st Duke of the Infantado

The title Duke of the Infantado was awarded to him by the Catholic Monarchs, Fernando II de Aragon and Isabel I of Castile, on 22 July 1475.

[citation needed] The old castle of Manzanares el Real was the residence of a part of the Mendoza family since the end of the 14th century.

The old castle of Manzanares el Real belonged to one the 1st Duke's aunts, a powerful and ruthless (elder) step sister of his father Íñigo, a duchess named Aldonza de Mendoza(circa 1380–1435).

When Aldonza died in 1435 the nephew, Íñigo, a Lasso de la Vega by his mother, and father of this 1st Duke, insisted over and over again to King Juan II of Castile, on becoming a count of what is now Manzanares el Real.

In the last third of the 15th century, the House of Mendoza decided to build a new palatial castle, larger and more luxurious, more fitting for the economic and political influence achieved by this family.