A native of Farmington, Maine, a young Greenwood had been dissatisfied with the bitter winter cold that froze his ears. The old method of wrapping an itchy wool scarf around one's ears was bulky and cumbersome. The fifteen-year-old Greenwood used coiled steel and had his grandmother sew on fur, thereby creating the world's first ear muffs. A few years later he patented an improved version and went into business. Eventually, he designed and built a factory that manufactured 400,000 pairs of earmuffs annually.
After his success at earmuffs, he went on to patent over 130 other useful products, including a steel-toothed rake, a wide-bottom tea kettle, a mechanical mousetrap, a spark-plug improvement, a shock-absorber (which became the basis of modern aircraft landing gear), and many others.
His native state of Maine annually celebrates his many achievements.
Story of his invention