Her name was Elizabeth Magie and her game was stolen by Charles Darrow.
Darrow went bankrupt after the 1929 Stock Market Crash, so when he saw his neighbors playing the game, he copied down the instructions, and published his own version of the game.
Then he sold it to the Parker Brothers who popularized the game. Darrow became a millionare within the year. Despite this, Hasboro currently lists him as the sole creator on their website.
Magie was amazing, and not just for her game. She liked to mock societal standards of the time through theater and even made national headlines mocking the institution of marriage. She supported herself until her mid 40s, proving that marriage was not the only option for women, before tying the knot herself.
Elizabeth Magie is attributed with this, “Girls have minds, desires, hopes, and ambitons.” Dont forget her name.