Upon the arrival of the Spanish during the 15th century what is now Antioquia Department was populated by numerous indigenous tribes, especially the Caribs, which according to archaeological findings began to extend their territory through the Caribbean region of the Antioquia Department and then moved south through the Cauca and Magdalena valleys.
Ten years later the Spanish conqueror Alonso de Ojeda entered with another group of Spanish conquerors and founded the village of San Sebastián de Urabá which function as a "business center" for the Spanish, this village was substituted later in duties with the village of Panama because of the constant attacks that received from the indigenous tribes.
San Sebastian de Uraba ruins are now located within the municipality of Necoclí, Antioquia Department.
While visiting as judge, Mon y Velarde introduced several reforms that were criticized by the general population.
Among his reforms were the reorganization of rental income from alcohol and tobacco, a new mining code that substituted the one governor Gaspar de Rodas had expedited in the 16th century, authorized the use of silver instead of gold for transactions and changed the agrarian structure of Antioquia which allowed the foundation of new villages, he also opposed that large amounts of land were maintained in possession by few individuals that did not dully exploited them.