The Pittsburgh Steelers: Steel Curtain. Joe Greene, L. C. Greenwood, Dwight White, and Ernie Holmes owned the line of scrimmage, anchoring the best defensive unit in NFL history. In 1976, they shut out five opponents and held three others from scoring a touchdown. Soon, they were known as the Steel Curtain, the most feared and respected front four ever to play the game. Photo credit: L. C. Greenwood.