The Gregorio Prieto Foundation was founded by the artist himself on 13 March, 1968 in the Cave of Medrano in Argamasilla de Alba, where Cervantes (Don Quixote's author) was imprisoned. A notary public witnessed the founding, and using the notarial instrument issued, the Foundation was registered with the Ministry of Education and Science, now the Ministry of Culture. It enjoys recognition as a private legal entity with general interest purposes. Its governing body is the Board of Trustees, which is responsible for the promotion and conservation of the artistic works of the painter Gregorio Prieto, as well as his manuscripts, correspondence, and other texts, and for undertaking cultural activities. The Gregorio Prieto Foundation bought a property in Valdepeñas, Ciudad Real, to house the Gregorio Prieto Foundation Museum, which was inaugurated by His Majesty the King Juan Carlos I on 19 February, 1990. Since 1996, all of the works of Gregorio Prieto owned by the Foundation have been inventoried at the Foundation’s museum in Valdepeñas.