Duke of Arcos  Duke of Arcos is a title in the Peerage of Spain that was created by Isabella I of Castile, on 20 January 1493, for Rodrigo Ponce de León, then Count of Arcos. The dukedom is among the first 25 titles which reached the rank of Grandee of Spain 1st Class, in 1520. Its name derives from Arcos de la Frontera in Cádiz.