Date: July 4, 1986
The Moment: It was clear that rap was quickly becoming an incredible force in pop music by the mid '80s. Record companies were getting to the point of not being able to get enough, especially where crossover with a white audience was concerned.
The stars lined up for RCA, though, in the summer of 1986: Aerosmith, a soaring '70s rock band hitting the skids in the '80s both creatively and logistically—having dealt with a bevy of inner-band conflict and Olympic-level drug abuse—needed a hit. Run-DMC simply needed a new hit, and wanted to achieve that next level of fame, bigger than rap, bigger than hip-hop, bigger than America. What emerged—thanks to Rick Rubin, who brought the idea to a reluctant Run-DMC—was "Walk This Way," a single released on July 4th, 1986, featuring the Queens-bred rap trio breaking beats and spitting rhymes over a scratched-up and mixed sample of Aerosmith's original mid '70s hit "Walk This Way."
The Impact: The song exploded. It became the first rap song to break the top five on the Billboard 100, charting all the way to the fourth spot (higher than Aerosmith's original ever did).
The Upshot: The track remains one of the most famous cover songs of all time, and the most early precedent of rock and rap acts mixing together successfully. It also spawned a memorable video, which tends to rank about as high and as often on rap lists, rock lists, and '80s lists as the song itself does.