Mary Walton was an independent American inventor. She is most famous for her activism in controlling pollution. In 1879 she invented a way for smokestacks to not pollute the air. She did this by having the emissions go to a water tank rather than in the sky. These water tanks could then be emptied into the sewage system.
Later in life, around 1890, she invented a way for elevated railroads to emit less noise. This was achieved by Walton making a model railway in her basement. She found storing the trains in a box-like frame of wood, painted with tar, lined with cotton and filled with sand would dampen the sound. She had both her ideas patented by the U.S. Government and sold them.
Sadly, I could find little about her personal life.
Portrait drawing and picture of train frame and smoke stacks: