Mary Walton

In 19th-century New York City, boarding house owner Mary Walton applied her mechanical engineering knowledge to address pollution caused by Manhattan’s rail system, resulting in vast improvements to the quality of life and health for her guests and fellow New York City dwellers.

Her first patent was for a water-based filtration system installed in chimneys to trap pollutants in a tank that would later be flushed. After the design received widespread support in New York and London, she then turned to addressing the noise and smoke from elevated trains. 

The result was a patented sound-dampening device for elevated railway systems. Her design used boxes lined with cotton and filled with sand to cradle the rails, muffling the sound emitted by the vibrations of the trains on the tracks. She sold her anti-noise pollution system to New York City’s Metropolitan Railroad, and it became an industry standard.