Reigned from February 6, 1922 to 1939. Born in 1857 in Desio, Italy as as Achille Ratti; died in 1939 He was made prefect of the Ambrosian Library, Milan in 1907; prefect of the Vatican Library in 1914; nuncio to Poland in 1918; cardinal and Archbishop of Milan in 1921. Before his election he wrote many studies and monographs on historical subjects, and was noted as an expert mountain climber. He is well known as a patron of learning and during his pontificate has encouraged the papal historians, Pastor and Carrere. He opened the Vatican Library to a group of American scholars, encouraged the Biblical Commission, and opened the Russian, Ethiopian, and Czechoslovakian colleges at Rome. He gave an impetus to the propagation of the Faith, dispatched nuncios to all the leading nations, celebrated the Holy Year of 1925, issued Encyclicals on the Peace of Christ in the Kingdom of Christ, the Institution of the Feast of Christ the King, the Catholic missions, and the persecution of the Catholic Church in Mexico. He presented General Nobile with a cross to be erected on the site of the North Pole, 1928. With his cooperation the seclusion of the popes in the Vatican came to an end on February 11, 1929 when the Lateran Treaty was signed establishing Vatican City, and a concordat was arranged with the Italian government securing recognition of the Catholic religion.