The parish already existed in the papal seal of Clement III in 1188, and San Lorenzo was the first patron of Montemerano. Documents from the middle of the thirteenth century confirm that this religious institution contributed money to the Crusades for the liberation of the Holy Land, a sign of the importance of Montemerano at the time. In 1382 the title of Parish Church was passed to the Church of San Giorgio, although San Lorenzo still stood as a church and a rectory. The bell tower is still the only one in the town to have had a clock (built in 1615), which was destroyed by lightning in 1834.