Pope Leo XIV will be the Catholic Church's 267th leader.
VATICAN CITY -- The temporary chimney atop the Sistine Chapel released a plume of white smoke on Thursday evening local time, signaling that the 133 cardinals working inside had reached a two-thirds majority to elect a new pope for the Catholic Church.
American Cardinal Robert Prevost was shortly thereafter announced as the 267th pontiff. He chose the name Leo XIV, a senior cardinal deacon announced.
The 69-year-old Chicago native is the first American pope and is seen as a diplomat in the church.
"This is the first greeting of the risen Christ. May the peace be with you," Leo said in Italian in his first remarks as pope. "This is the peace of the risen Christ."
(The Associated Press and ABC News contributed to this report.)
Pope Leo XIV - history-making, the first American Pope. Now, David Muir reports from the Vatican in the breaking, new "20/20" special edition. Watch the premiere of "The American Pope | Leo XIV" tonight at 9/8c on ABC. Stream on Hulu and Disney+
Black smoke spewed from the Sistine Chapel chimney after the 1st conclave vote Wednesday, meaning a new pope has not yet been selected.
Cardinals will continue to vote until white smoke appears, meaning a pope has been selected.
The balloting process for the papal conclave may be shrouded in secrecy, but it is straightforward.
Each conclave member writes his choice on a paper ballot slip and folds it once in half. He then carries it aloft between two fingers as he walks to the altar.
The slip is then deposited into a special urn used only for the balloting process.
Conclave members are instructed to write their votes "as far as possible in handwriting that cannot be identified as his" to ensure anonymity.
Any conclave member who cannot make it in person to the Sistine Chapel due to illness or infirmity casts his ballot from this room in the Domus Marthae Sanctae. Those ballots are placed in a lockbox and carried to the Sistine Chapel.
Three scrutineers then count the votes by affirming what is written on each ballot and announcing it to the conclave, which allows the cardinals to record the votes themselves.
The first candidate to secure two-thirds of the votes is elected as the next pope.
The prospect of an American becoming pope is "very unlikely," according to Dr. Miles Pattenden, a historian of the Catholic Church and a lecturer of history at Oxford University in England.
"There has traditionally been a lot of wariness about a pope from the Anglosphere," Pattenden said. "I shouldn't think that the current circumstances change that, especially now with the tensions between the Vatican and the Trump administration."
An American cardinal, Robert Prevost, has nevertheless started to emerge as a front-runner for the papacy, according to Father James Martin, a papal contributor for ABC.
-ABC News' Bill Hutchinson and Megan Forrester
The master of ceremonies has called "extra omnes" -- ordering all those who are not cardinal electors to exit the Sistine Chapel prior to the start of the conclave.
The door to the Sistine Chapel closed as the cardinals begin the process of choosing the new pope.
