Twenty years ago this month, N.W.A. were doing good. Songs like "Fuck the Police" and "Gangsta Gangsta" had traveled from the inner-city streets of Southern California to backyard barbecues in white suburban towns. While the group was on a nationwide tour, their album Straight Outta Compton sold its millionth copy. They were making it. But it took the promotional touch of the F.B.I. to really blow them up into megastars.

"A song recorded by the rap group N.W.A. on their album Straight Outta Compton encourages violence against and disrespect for the law enforcement officer and has been brought to my attention," wrote the agency's assistant director Milt Ahlerich, in a soon-to-be-famous August 1989 letter. "I understand your company recorded and distributed this album and I am writing to share my thoughts and concerns with you."

Ruthless Records publicist Phyllis Pollack forwarded the letter to every journalist on her rolodex. The Village Voice ran a cover story. The group's signature L.A. Raiders caps became a nationwide fashion phenomenon. N.W.A. was the biggest thing in music.

"I knew the letter would be pure gold for N.W.A." said Ruthless Records cofounder Jerry Heller, in his 2007 memoir, Ruthless. "What better imprimatur could a rap group have than hate mail from the F.B.I.?"