Pope Leo grew up in suburban Dolton in Chicago, where he attended Mass and elementary school at St Mary of the Assumption.
He later studied theology at the Catholic Theological Union of Chicago in Hyde Park and taught in local Catholic schools, including at St Rita High School, according to the school.
"We are overjoyed that someone who is beloved and known to us is now the beloved leader of the whole entire church," said Barbara Reid, a Dominican sister and president of the Catholic Theological Union.
John Doughney, a fellow St Mary's grade school graduate from 1969, remembers the pope as a "friend to everyone" and a "kind, caring, compassionate young man".
"Even when he was 12 and 13, it was apparent to all of us that he knew what his calling was," he said.
"It would've shocked all of us if he didn't go into the priesthood. We're so proud of him."
Linda Eickmann, 62, was also born and raised in Dalton and attended St. Mary's.
When she saw the news of the new pope on TV, she screamed with joy.
"How cool is that?" she said, "A pope from my elementary school, from my town. It's unreal."
Ms Eickmann remembered Prevost's family as being deeply involved in the St Mary's community, where everyone knew their names.
They ran sloppy joe sales to raise money for the school, and all their sons were altar boys, including the young Pope Leo.
Reporting with AP