HISTORY. Guinea-Bissau formerly, Portuguese Guinea, on the coast of Guinea, was discovered in 1446 by Nuno Tristão. It became a separate colony in 1879. It is bounded by the limits fixed by the convention of 12 May 1886 with France. On 10 Sept. 1974 Portugal formally recognized the independence of Guinea-Bissau. Guinea-Bissau became a member of the UN in Sept. 1974.