Sixtus IV, pope (originally Francesco della Rovere), was born July 22, 1414, it is said of the family of Rovere; but, according to the bat historians, he was the son of a poor fisherman. He was brought up by cardinal Bessarion, and entered the Order of the Minorites, whose head he eventually became. Paul II made him a cardinal, and he succeeded him as pope, Aug. 9, 1471. His pontificate was occupied with schemes of reform, and with expeditions against the Turks; but he also engaged earnestly in efforts for the maintenance of the privileges of the Holy See, laying the city of Florence under an interdict, and finally Venice likewise. Being of a weak and unprincipled character, he wasted the public and papal resources in his extravagant intrigues. He died at Rome, Aug. 18, 1484, and was succeeded by Innocent VIII. It was he who built the Sistine Chapel and founded the Festival of the Conception of the Virgin. There are a few theological treatises by him, also some Letters, etc., for which see Hoefer, Nouv. Biog. Generale, s.v.