Haynes is remembered as a pioneer of the American automobile, and as the creator of the first automobile design viable for mass production. He is credited as being one of those primarily responsible for the rapid growth of the natural gas industry in Indiana, a boom that made northern Indiana one of the leading industrial regions of the United States. He is also remembered for his development of stainless steel and stellite, materials that are commonly used across the world today. Stellite remains an important metal, as its ability to withstand high temperatures has made it a component in American spacecraft. In July 2015, he was inducted into the 75th class of the Automotive Hall of Fame in Detroit, Michigan.