The longest papal conclave in history lasted nearly three years—specifically 1,006 days. It took place from November 1268 to September 1271 in the city of Viterbo, Italy. This conclave was held to choose the successor of Pope Clement IV. The lengthy deadlock was due to deep divisions among the cardinals, particularly between factions loyal to the papacy and those supporting the Holy Roman Empire. The situation became so drawn out that the citizens of Viterbo locked the cardinals in the meeting room to pressure them into making a decision, which is where the term "conclave" (meaning "under lock and key") originates from. The conclave ended with the election of Pope Gregory X.
