The one we can thank for Popes wearing white, though all he was doing was continuing to wear the white habit of the Order of Friar Preachers, even as Pontiff. In that case, I suppose we have Gregory XIII (Pope from 1572-1585) to thank for continuing the tradition.
But Papa Ghislieri can also be thanked for so many other things:
- His determination to put into effect the decrees of the Council of Trent (dare we say, he lived "in the spirit of Trent"?).
- Following the Council's decrees, he saw to the publication of the Roman Catechism (1566), the Roman Breviary (1568), and the Roman Missal, a.k.a. the "Sacramentary" here in the United States (1570).
- Declared St. Thomas Aquinas a Doctor of the Church on April 11, 1567.
- After the victory at Lepanto of a coalition of ships from Spain, Venice, and the Papal States over the Ottomans was attributed by Pius to Our Lady's intercession, he instituted the Feast of "Our Lady of Victories" on October 7 (the date of the battle). The name of the feast was later changed by his successor to "Our Lady of the Rosary".
Pope St. Pius' tomb is there for the world to see in the Basilica of St. Mary Major. His tomb is located in the "Sistine Chapel" (named so because it was built to house the tomb of Pope Sixtus V, who was the successor to Gregory XIII following Pius V; got that?). It's appropriate that Pius rests here, since it was Pius who named Felice Peretti (the future Sixtus V) a Cardinal in 1570. Though it is kind of amusing that the Dominican Pius V spends eternity in a chapel built for the Franciscan Sixtus V. You can learn more about the chapel by visiting the website for Santa Maria Maggiore.