The name ''Kiribati'' was adopted in 1979 at independence. It is the Gilbertese rendition of ''Gilberts'', the plural of the English name of the nation's main archipelago, the ''Gilbert Islands''. It was named ''îles Gilbert'' (French for ''Gilbert Islands'') in about 1820 by Russian admiral Adam von Krusenstern and French captain Louis Duperrey, after the British captain Thomas Gilbert. Gilbert and captain John Marshall sighted some of the islands in 1788, while crossing the "outer passage" route from Port Jackson to Canton. Both von Krusenstern's and Duperrey's maps, published in 1824, were written in French. In French, the Northern Islands were until then called « ''îles Mulgrave'' » and Byron Island was not part of them.