February 11, 1929: The Lateran Treaty is signed, establishing Vatican City.

This treaty was signed in the Lateran Palace between Italy’s Victor Emmanuel III (represented at the agreements by Benito Mussolini) and Pope Pius XI (represented by Pietro Gasparri). The Lateran Treaty first, recognized the sovereignty of the Holy See and Vatican City; second, established Catholicism as the religion of Italy; third, settled the financial dispute between the two states and the “Roman Question”. 

Four years later, the controversial Reichskonkordat with Nazi Germany would be signed.