From the middle of the 18th century, and as part of the legislation on the Matrícula de Mar, the compulsory registration of all national ships was instituted by the State Administration. The Registro de Matrícula established the initial registration of each ship, and it was controlled by the Marine Authorities. The registration number was unique for each ship, allowing them to be clearly identified. The information contained in the register varied over time, but generally included the name and technical characteristics of each ship, the place and date of construction, as well as the name of the builder. Information was also included on the owner or owners of each ship, as well as its vicissitudes, especially their purchase / sale operations. Each Maritime District established its own registry and within these registries different lists were organized. The list of sailing ships used in commercial navigation, that of steamships, that of fishing ships and that of internal traffic ships in each port, among others.