Meanwhile, a quick look at the history of the IQ test would show that it was not widely available to Americans until Monroe was in her 20s, and even then, the test was for children. And poor Monroe, doomed to play a "dumb blonde" until her death, was also sensitive about the fact that she didn't finish high school. Add that to her marriage at 16, and you realize that even if she was a genius, she never really had a chance to prove it in an academic sense. That said, she definitely made some savvy business decisions, even starting her own production company to force studios to give her more creative control.
Scott Fortner, a curator of The Marilyn Monroe Collection, told Snopes that while she was "more into books than shoes" and had an extensive library, "There were no records present of her having been [IQ] tested." So she was probably smart, but we'll have to live with the fact that we can't easily quantify her smarts with a numerical score.