June 16, 1846 - Giovanni Maria Mastai Ferretti Named Pope Pius IX

On June 16, 1846, Giovanni Maria Mastai-Ferretti was named Pope Pius IX. He is remembered for the longest pontificate in history, lasting 31 years. He also declared the Immaculate Conception, the idea that Mary was free from original sin at the moment of conception, official church dogma. He was also Pope when the First Vatican Council declared the infallibility of the pope, the idea that the pope, when speaking to the entire church on a matter of morality from Scripture, is protected by the Holy Spirit from speaking incorrectly.