This paper explains the process by which the Bank of Spain became a national bank, first by obtaining the monopoly of note issue in 1874 and then by extending its sphere of financial action by creating the country's only network of bank branches before 1900. The implementation of a “unified or national banknote” in 1884 and the creation of a system of free transfers for its clients were also decisive steps towards the Bank's transformation from a local Madrid-based institution into a Spanish national institution. The paper also argues that the transformation of the Bank of Spain into a genuine national financial institution contributed to the modernization of the Spanish administrative structure.