Almost a decade before Beverly Johnson graced the cover of American Vogue, thus becoming the first African American woman to do so, there was Donyale Luna, the first black woman to do so across the pond. The Detroit-born (super)model appeared on the March 1966 cover of British Vogue at the age of 20, becoming an instant sensation in the fashion world. Before Luna came along, modelling was a job mainly done by extremely attractive socialites and doe-eyed Brits like Jean Shrimpton.
“Donyale Luna, as she calls herself, is unquestionably the hottest model in Europe at the moment,” wrote Time magazine shortly after the cover’s release. She began modelling a year prior to that, and had already appeared on the cover of Harper’s Bazaar — although in an illustration only — but very soon hit a wall, after Bazaar’s advertisers in the southern states pulled their advertising in protest of her photographs (shot by Avedon!) appearing in the magazine. Unlike America, Britain welcomed her with open arms. 
As far as the infamous cover (photographed by that epitome of swinging London, David Bailey) goes, there are two versions of the story. One rumour claims that Bailey made her hide her features with her hand, in order to hide her ethnicity. The other explanation for the curious pose was that Bailey was highly influenced by Picasso’s compositions, and Donyale had the features — those ginormous eyes — to pull it off. I like to believe the latter. The issue was titled “Eye on the International Collections,” and perhaps she was the eye. 
The editorial was young and modern: oversized eyelashes, brightly coloured tunics by Jean Patou, flowy romantics frocks by Pierre Cardin and Yves Saint Laurent’s minis. “Once again it’s the year of the fabric makers. More inventive, more beautifully coloured and textured than ever,” said the magazine.

Britain, at the time, was at its most inventive — heaps above American Vogue, until Diana Vreeland imported most of the British staff and models. Subsequently, Donyale did quite a bit of work for the American counterpart, but she never got another cover. Neither did any black model until Beverly Johnson in 1975. 
PS. Sadly the story of Donyale’s life was not a happy one. 
Further reading: “The Tragic Tale of Donyale Luna” by Ben Arogundade, Telegraph (November 11, 2012).