In her post-election tell-all "What Happened," Hillary Rodham Clinton shares an anecdote about writing to NASA as a uniquely determined young teenager.

But the story doesn't go as you might expect. Unlike today's inspiring tales of kids writing to NASA and receiving encouragement, the future Secretary of State's experience was far more grim.

"I don't know what it's like for other women, but growing up, I didn't think that much about my gender except when it was front and center," she writes.

"Like in 8th grade, when I wrote to NASA to say that I dreamt of becoming an astronaut," she continues, "and someone there wrote back: Sorry, little girl, we don't accept women into the space program."

Clinton wrote the letter sometime around 1960. It wasn't until 1978 that the first female astronaut candidates were admitted into the program.

A NASA representative told CNBC Make It that the letter was "a reflection of the early 1960's culture when astronauts were required to be military test pilots. We believe NASA today embraces the race and gender diversity that reflects America and its values."