answer:From Wikipedia: “The original dusters were full-length, light-colored canvas or linen coats worn by horsemen to protect their clothing from trail dust. These dusters were typically slit up the back to hip level for ease of wear on horseback and were the recommended “uniform” for Texas Rangers. Dusters intended for riding may have features such as a buttonable rear slit and leg straps to hold the flaps in place. For better protection against rain, dusters were made from oilcloth and later from waxed cotton.”