Margaret Eloise Knight (1838-1914) was the most famous woman inventor of the 19th century. She’s build many inventions during her lifetime, but what she is most well-known for is a machine she built when she was 30, which folded and glued paper to create a flat-bottomed paper bag. The product was popular — so popular, in fact, that a man stole the idea to patent himself. When Knight took him to court for patent interference, he argued that a woman “could not possibly understand the mechanical complexities.” Knight won her case by providing proof that she had designed the machine, earning herself the right to patent her machine. Over the course of her career, Knight invented over 100 different machines and holds a whopping 87 US patents, including a rotary engine, a shoe-cutting machine, and a window frame with a sash. But if the true test of an invention is its staying power, then Knight’s paper bag — still used today — is proof of her incredible gifts.