In this text we define and synthesize some key ideas of the National Gallery of Painting - Academy of Fine Arts of Lisbon, since the beginning of its collection in 1834 with the dissolution of the religious orders, until the opening in 1884 of the National Museum of Fine Arts and Archaeology. Under review are 50 years of efforts carried out by several players, mainly the marquis de Sousa Holstein, Deputy Inspector of the Academy, in favour of the organization, conservation, exhibition, study, promotion, dissemination of its collection, in addition to the enrichment through transfers, purchases or donations which were the source of the most important public museum of art of Portugal.