Little is known of Leo’s life before he entered the pontificate on Sep 29, 440 CE. The Liber pontificalis relates that Leo was born in Tuscia, the son of a Quintianus who is otherwise unknown. It seems that Leo served as archdeacon under Sixtus III (432–440 CE), in which role he would have received valuable training for the office of bishop. This was a common career path in the papal service. From Sixtus III, he inherited an ongoing major bui…