The papal conclave held from 18 to 20 February 1878 saw the election of Vincenzo Pecci, who took the name Leo XIII as pope. Held after the death of Pius IX, who had had the longest pontificate since Saint Peter, it was the first election of a pope who would not rule the Papal States. It was the first to meet in the Apostolic Palace in the Vatican because the venue used earlier in the 19th century, the Quirinal Palace, was now the palace of the king of Italy, Umberto I.

In the papal conclave held from 14 to 16 June 1846, Giovanni Maria Mastai Ferretti, Bishop of Imola, was elected on the fourth ballot to succeed the recently deceased Gregory XVI as pope. He took the name Pius IX. Of the 62 members of the College of Cardinals, 52 assembled in the Quirinal Palace, one of the papal palaces in Rome and the seat of two earlier 19th century conclaves. The conclave was the last to elect a ruler of the Papal States, the extensive lands around Rome and Northern Italy which the Catholic Church governed until 1870.