Bl. Pius IX

Subject and later the last sovereign of the Papal States, finally becoming an Italian citizen. Defined the dogmas of Immaculate Conception and papal infallibility. Issued the controversial Syllabus of Errors (1864). Opened the First Vatican Council (1869). Lost the Papal States to Italy (1870).

Longest-reigning pope since Peter (c. 30–64); longest verified reign. First pope to be photographed. During his pontificate, Augustinian friar Gregor Mendel published the "Experiments on Plant Hybridization" and Charles Darwin published On the Origin of Species. At that time, no high-level Catholic Church pronouncement attacked head-on the theory of evolution as applied to non-human species.