"I Walk the Line" is a song written and recorded in 1956 by Johnny Cash. After three attempts with moderate chart ratings, it became Cash's first #1 hit on the Billboard charts, eventually reaching #17 on the US pop charts. The song remained on the record charts for over 43 weeks and sold over two million copies. It was the title song for a 1970 film starring Gregory Peck and a 2005 biopic of Cash starring Joaquin Phoenix. The song captures Johnny Cash's "boom-chicka-boom" sound by Johnny putting a dollar bill in the neck of his guitar.

Source: Wikipedia