On December 28, 1938, the silent-film star Florence Lawrence dies by suicide in Beverly Hills. She was 52 years old. Though she was best known for her roles in nearly 250 films, Lawrence was also an inventor: She designed the first “auto signaling arm,” a mechanical turn signal, along with the first mechanical brake signal. She did not patent these inventions, however, and as a result she received no credit for–or profit from–either one.

Born Florence Bridgewood in 1886 in Hamilton, Ontario, Lawrence entered show business when she was very young: her mother, a vaudeville actress named Lotta Lawrence (née Charlotte Bridgewood), brought baby Florence on the road with her, sending her onstage as “Baby Flo, The Child Wonder Whistler.” Lawrence got her first movie role in 1907 (“Daniel Boone“) and in 1910 she became the first actress to headline a film by name. (Before that, she was simply known as “The Biograph Girl,” for the name of her film studio.)

Because she was such a successful actress, Lawrence was able to buy her own car–a rarity in the early 20th century, when cars were still luxury items. She adored driving and loved learning all she could about the way automobiles worked. “A car to me is something that is almost human,” she said, “something that responds to kindness and understanding and care, just as people do.” In 1914, she developed a mechanical signaling arm that, with the press of a button, raised or lowered a flag on the car’s rear bumper that told other drivers which way a car was going to turn. After that, Lawrence devised a rudimentary brake signal that worked on the same principle: when a driver pressed the brakes, a “STOP” sign flipped up from the back bumper. These inventions were enormously important, obviously–today, every car on the road has electrical turn signals and brake lights–but because she never bothered to file patents for her work, Lawrence never got the recognition she deserved. (Not that it would have made much difference: her mother, also an inventor, patented the first electrical windshield wipers in 1917 and never got much credit either.)

After Lawrence was badly burned while rescuing another actor from a studio fire in 1915, she had a hard time finding work. Her first and second husbands died tragically, and she was divorced from her third less than a year after marrying him. She also had a rare bone-marrow disease that caused her a great deal of pain. Lawrence’s life came to an early end in 1938, when she poisoned herself in her Beverly Hills home.