Vogue initially began as a bimonthly publication in 1892 and at the turn of the century in 1909 when Condé Nast acquired the title, subscription rates began increasing. Editor, Diana Vreeland, directed the emphasis of the magazine towards youth culture and the energy of the sexual revolution of the 1960s, and launched the career of young modelets such as Twiggy and Penelope Tree.
During the 70s the emphasis shifted once more with the arrival of a new editor-in-chief, Grace Mirabella, where major changes were corresponding to the shifting trends of their target audience's lifestyles.
Current Vogue's editor-in-chief, Anna Wintour took reign in 1988 where she has protected the prestige of the influential fashion publication. Wintour has made fashion more accessible thus increasing readership.
Good for you for reading Vogue when you were 12-15 though. When I was that age, I wasn't even reading Teen Vogue, I was reading stuff like Seventeen :x