Pope Pius IX -Longest-reigning elected pope

Pope Pius IX (13 May 1792 – 7 February 1878), born Giovanni Maria Mastai-Ferretti, reigned from 16 June 1846 to his death in 1878. He was the longest-reigning elected pope in the history of the Catholic Church — over 31 years. During his pontificate, he convened the First Vatican Council (1869-1870), which decreed papal infallibility, but the council was cut short due to the loss of the Papal States. Pius IX defined the dogma of the Immaculate Conception of the Blessed Virgin Mary, meaning that Mary was conceived without original sin. Pius IX also granted the Marian title of Our Mother of Perpetual Help, a famous Byzantine icon from Crete entrusted to the Redemptorist priests

  

He was also the last pope to rule as the Sovereign of the Papal States, which fell completely to Italian nationalist armies in 1870 and were incorporated into the Kingdom of Italy. After this, he was referred to - chiefly by himself - as the "Prisoner of the Vatican". After his death in 1878, his canonization process was opened on 11 February 1907 by Pope Pius X and it drew considerable controversy over the years. It was closed on several occasions during the pontificates of Pope Benedict XV and Pope Pius XI. On 7 December 1954, Pope Pius XII re-opened the cause and Pope John Paul II proclaimed him Venerable on 6 July 1985. He was beatified after the recognition of a miracle on 3 September 2000 together with Pope John XXIII, and was assigned the liturgical feast day of February 7 which is the date of his death.