The first written use of the name in Spanish can be traced to ''La Argentina'', a 1602 poem by Martín del Barco Centenera describing the region. Although "Argentina" was already in common usage by the 18th century, the country was formally named "Viceroyalty of the Río de la Plata" by the Spanish Empire, and "United Provinces of the Río de la Plata" after independence.