This sailor and military man from Burgos was in charge of the Ministry of the Navy between 1783 and 1795. He did extraordinary work organizing and promoting shipbuilding, following in the wake of José Patiño y Rosales and the Marquis of Ensenada. In 1793 he published the "Naval Ordinances" containing the naval rules and codes of conduct. He also improved officer training, setting up mathematics courses, upgrading libraries, and expanding study and teaching materials at the College of Medicine and Surgery in Cádiz. Under his mandate, the Hydrographic Depot was founded to study and manage hydrography issues, as a successor to the House of Commerce. The "Spanish Maritime Atlas" was created there by Vicente Tofiño, commissioned by Valdés as a hydrographic atlas of the peninsula's coasts, adjacent islands, and Africa. A library and catalog were also established, along with a store for nautical charts and other kinds of maritime information.
His work was key to scientific development as it supported expeditions such as Malaspina and Antonio de Córdoba's voyage to the Strait of Magellan.
The work is by the Murcian painter Rafael Tegeo, a famous portraitist and member of the San Fernando Royal Academy of Fine Arts. It is a copy of a Francisco de Goya original which is now in a private collection. It depicts the uniform of a squadron leader in the Spanish Royal Navy with a gold-trimmed, blue dress coat over a gold-buttoned, crimson vest. The coat bears the cross and symbol of the Order of Malta.