Kiritimati was discovered to Europeans by the Spanish expedition of Hernando de Grijalva that charted it as Acea. This discovery was referred by a contemporary, the Portuguese António Galvão, governor of Ternate, in his book Tratado dos Descubrimientos. Captain James Cook visited it on Christmas Eve in 1777. It was claimed by the United States under the Guano Islands Act of 1856.