The first black model to appear on the cover of Vogue was Beverly Johnson, August 1, 1974. A few weeks later, I was born. Clearly, things were looking up in the world!
From page 212 of In Vogue: An Illustrated History of the World's Most Famous Fashion Magazine by Norberto Angeletti and Alberto Oliva. (The book, incidentally, is a hefty tome, lavishly illustrated with gorgeous, stunning, and breath-taking photos from the magazine. Lots of fun and inspiration for both fashionistas and photographers.)