From the LCMS website:
One of the great leaders in Europe at the close of the sixth century, Gregory served in both the secular and sacred arenas of his era. As mayor of Rome, he restored economic vitality to his native city, which had been weakened by enemy invasions, pillage, and plague. After he sold his extensive properties and donated the proceeds to help the poor, he entered into full-time service in the Church. On September 3, 590 A.D., Gregory was elected to lead the church in Rome. As Bishop of Rome he oversaw changes and growth in the areas of church music and liturgical development, missionary outreach to northern Europe, and the establishment of a church-year calendar still used by many churches in the western World today. His book on pastoral care became a standard until the 20th century.