When did Carrie Underwood become a country singer?

Carrie Underwood rose to fame as the winner of the fourth season of American Idol in 2005. Following her victory, she signed with Arista Nashville and released her debut album, "Some Hearts," in November 2005. "Some Hearts" went on to become the best-selling solo female debut album in country music history and one of the best-selling country albums of all time. With this album and follow-up albums, Carrie Underwood established herself as a successful country singer.