August 1950: A 24-year-old Marilyn, wearing a simple button-down shirt monogrammed with her initials, leans against a tree in Los Angeles' Griffith Park for LIFE photographer Ed Clark. The negatives for these photos were recently discovered during our ongoing effort to digitize LIFE's immense and storied photo archive, including outtakes and entire shoots that never saw the light of day. Click through to see more stunning shots of Marilyn, plus the reason why they may never have been published...