At St. Mary of the Assumption school in Chicago’s southern suburbs, Robert Prevost was quiet, kind and studious. Mostly, he wanted to be a priest. It was the 1960s, and the parish school was a hub for Catholic families in the working-class neighborhood.

The Roman Catholic cardinals gathered at the Vatican in Rome have chosen a new pope to lead the church’s 1.4 billion faithful, announcing their decision on Thursday with a swirl of white smoke from a smokestack above the Sistine Chapel.

In a tradition that scholars date to the 19th century, smoke released from a chimney will be colored white if the cardinals have made a decision, or black if they remain deadlocked.