Mary Walton received U.S. Patent No. 221,880 for her 'Improvement in Locomotive Smoke-Stacks'. This invention aimed to reduce the air and noise pollution generated by locomotives. The design involved water-filled deflectors that captured soot and other pollutants, preventing them from being released directly into the atmosphere. This highlighted her understanding of the growing problems of pollution from the industrial revolution.

Walton was granted U.S. Patent No. 249,442 for her 'Improvement in Locomotive Furnaces'. This invention focused on further mitigating air pollution by improving the combustion process within the locomotive furnace. The invention was likely complementary to her smoke stack design, working together to reduce emissions.