The following comes from the Patron Saints Index:
Born to an Italian peasant family. Educated at Bergamo and the Pontifical Roman Seminary. Ordained on 10 August 1904. Secretary to the bishop of Bergamo, Italy from 1904 to 1914, during which he wrote the basis for his five-volume biography of Saint Charles Borromeo. Served in World War I in the medical corps, and as a chaplain. Worked in Rome, Italy after the war, and reorganized the Society for the Propagation of the Faith. Titular archbishop of Areopolis on 3 March 1925. Vatican diplomatic representative to Bulgaria on 16 October 1931, then to Turkey and Greece on 12 January 1935. Titular archbishop of Mesembria on 30 November 1934. Papal nuncio to France on 23 December 1944 where he mediated between conservative and socially radical clergy. Created cardinal on 12 January 1953, and patriarch of Venice, Italy on 15 January 1953. Elected 261st pope on 28 October 1958.
As pope he stressed his own pastoral duties as well as those of other bishops and clergy. Promoted social reforms for workers, poor people, orphans, and the outcast. He advanced cooperation with other faiths and traditions including Protestant, Greek Orthodox, Church of England, and even Shinto. In April 1959 he forbade Catholics to vote for parties supporting Communism. His encyclical, Mater et Magistra of 14 July 1961 advocated social reform, assistance to underdeveloped countries, a living wage for all workers, and support for socialist measures that promised real benefit to society.
He nearly doubled the number of cardinals, making the college the largest in history. On 25 January 1959, he announced his intent to call a council to consider ways to renew the Church in the modern world, promote diversity within the unity of the Church, and consider reforms promoted by ecumenical and liturgical movements. Convening the council, known as Vatican II, on 11 October 1962, was the high point of his reign.
His heartiness, his overflowing love for humanity individually and collectively, and his freshness of approach to ecclesiastical affairs made John one of the best-loved popes of modern times.