The archive is one of the oldest institutions in Portugal, since its installation in one of the towers of the castle in Lisbon, occurring during the reign of Ferdinand I, and likely in 1378 (the date where the first testimonal originated). The archive served as the King’s and nobilities’ reference, with documents supporting the administration of the kingdom and overseas territoies, and documenting the relationships between the State and foreign kingdoms.

Among the significant collections at the Arquivo are items relating to the Portuguese explorations and discoveries in Africa, Asia and Latin America. The Corpo Cronológico (Chronological Corpus), a collection of manuscripts on the Portuguese discoveries, was inscribed on UNESCO’s Memory of the World Register in 2007 in recognition of its historical value “for acquiring knowledge of the political, diplomatic, military, economic and religious history of numerous countries at the time of the Portuguese Discoveries.” Another item relating to the Portuguese discoveries, the Carta de Pêro Vaz de Caminha (Letter from Pêro Vaz de Caminha), was also inscribed on the Memory of the World Register in 2005. This letter is the first document describing the land and people of what became Brazil.