High Quality Content by WIKIPEDIA articles! The Durango and Silverton Narrow Gauge Railroad (D SNG) is a narrow gauge heritage railroad that operates 45 miles (72 km) of 3 ft (914 mm) track between Durango and Silverton, in the US state of Colorado. The railway is a federally designated National Historic Landmark and is also designated by the American Society of Civil Engineers as a Historic Civil Engineering Landmark.