Apple's iTunes has sold its 10 billionth tune.

Apple said Thursday that its online music store crossed the threshold Wednesday when 71-year-old Louie Sulcer of Woodstock, Ga., bought "Guess Things Happen That Way" by Johnny Cash.

iTunes had promoted the 10 billion mark and celebrated the milestone by giving Sulcer a $10,000 iTunes gift card.

Introduced in 2003, iTunes became the top overall music retailer in the U.S. in 2008.