Robert Prevost's historic election as the first American pope followed a centuries-old papal conclave held within the Sistine Chapel, where 133 cardinal-electors gathered in solemn secrecy to choose the 267th leader of the Roman Catholic Church.

The election of Pope Robert I, formerly Cardinal Robert Prevost, marks a historic milestone for the Catholic Church, not only because he is the first American to ascend to the papacy, but also because of the deeply traditional process that ushered in his pontificate.

The conclave officially began on Wednesday afternoon, as the cardinal-electors - all under the age of 80 - entered the Sistine Chapel after celebrating a special Mass.

The ritual was steeped in pageantry: scarlet cassocks, Latin chants, oaths of secrecy, and the dramatic closing of the chapel doors signaled the start of the secluded proceedings.