"Rick Rubin has a larger looming presence on this album than his 'thank you' deserves. He asked 'Why can't more people cover U2 songs?' And it's because, with all the great sounds and arrangements, you can forget that there isn't a song there."
- Bono on Rubin's influence on Songs of Innocence
The song Heartland is about a trip Bono and Adam made after the Joshua Tree tour through America by car, they passed many placed and states and Heartland contains phrases of Bono's journey of that trip.