A list of gauge railways in the United States. Apart from historical railways, it is commonly used in underground coal mines. Also, in the past, this gauge had been a popular choice for urban mass transit systems (see table below). Railroads See also Narrow gauge railroads in the United States Heritage railway 2 ft gauge railroads in the United States 2 ft 6 in gauge railroads in the United States 3 ft gauge railroads in the United States Three foot six inch gauge railways in the United Kingdom References