Pope Francis will be making his first major mark on the U.S. church through the Archdiocese of Chicago.

Church analysts are closely watching for the pope to announce his choice of a successor to Chicago Cardinal Francis George. The Roman Catholic archdiocese is the third-largest in the U.S. and has produced leaders who have gone on to shape national debate inside and outside the church.

George submitted his resignation two years ago at age 75 as expected, so the pope could decide how much longer he would serve as archbishop. George's spokeswoman says it could be six months to a year before the Vatican announces a successor.

Analysts say the pope's choice for Chicago will be the clearest signal yet of the direction he hopes to move American church leaders.