On this day we observe the feast of Bl. Pope Pius IX.
Giovanni Maria Mastai-Ferretti, born in Senigallia on May 13, 1792, was elected Pope on June 16, 1846. The longest reigning Pope in history died on Feb. 7, 1878.
"He had a difficult pontificate, but precisely because of that he was a great Pope, certainly one of the greatest."
--from "Pope Pius IX",  L'Osservatore Romano, Weekly Edition in English 6 September 2000.
Not all would agree. For an account of the political upheaval and religious turmoil that marked Pius IX's papacy, see Saints and Sinners: A History of the Popes,  by Eamon Duffy, Yale University Press, 2006. (Search term: Pius IX.)
The loss of the Papal States, the Syllabus of Errors, and infallibility were among the divisive issues.
The convert from Anglicanism, Archbishop Henry Edward Manning,  was a leading figure of the Ultramontanes who advised Pius IX to issue the encyclical Quanta Cura to which was attached the Syllabus of Errors. 
"On the feast of Sts Peter and Paul 1867, . . . Pio Nono announced the summoning of a general council, to begin on 8 December 1869. Manning and other leading Ultramontane bishops took a solumn vow at the tomb of St Peter to work for the definition of papal infallibility at this, the First Vatican Council."
--Duffy, p. 230.
For a description of the Council and an engraving of the scene, see pp. 231-232.
"La tradizione son' io. Pius' magnificently arrogant aphorism laid bare both the attraction and the historical poverty of the infallibilist case. . . .The final vote on the infallibility decree took place on 18 July 1870. Fifty-seven members of the minority . . . had left Rome the day before so as not to have to vote against a measure they now knew would go through by an overwhelming majority. In the event, 533 bishops voted for the decree, only two against. One of these two was Bishop Fitzgerald of Little Rock, Arkansas in the USA. When the Pope finally read out the decree, Fitzgerald left his place, knelt at the Pope's feet and cried out, 'Modo credo, sancte pater' ('Now I believe, Holy Father')."
Pope Pius IX, along with Pope John XXIII, Archbishop Tommaso Reggio, Father William Chaminade, and Abbot Columba Marmion, was beatified  by Pope John Paul II on Sept. 3, 2000. "He was much loved, but also hated and slandered."
For an explanation of the opposition to the beatification, see Making Saints: How the Catholic Church Determines Who Becomes a Saint, Who Doesn't, and Why, by Kenneth L. Woodward, Touchstone, 1996.
For additional information on the controversial beatification, see the following articles:
"The Beatification of Pope Pius IX,"  by John W. O'Malley, S.J., America, Aug. 26, 2000.
"Pope of Infallibility Set for Beatification",  by John L. Allen Jr, NCR, Sept. 1, 2000.
"No! No! Pio Nono - Beatification of Pius IX," Commonweal, August 11, 2000.