for new winter activities such as the expansion of the town-operated ski hill could permanently improve Silverton's winter tourism. The town has also become well known for its winter backcountry activities such as snowmobiling, ice climbing, and backcountry skiing. Both the town and the Durango and Silverton Narrow Gauge Railroad were designated a National Historic Landmark in 1961. In 1966, the entire town was placed on the National Register of Historic Places. These boundaries were expanded in 1997 with the addition of the Shenandoah-Dives mill and other historical structures. Notable disasters The area surrounding Silverton has been the scene of several well-documented disasters, many of them due to avalanches and mining accidents. 1906 avalanches Five miners perished in a slide at the Sunnyside mine in January 1906. Only a few months later, twelve miners were killed in another slide at the Shenandoah Mine, making it one of the most deadly slides in the history of Colorado. 1918 influenza pandemic The Spanish Flu arrived in Silverton near the end of October, 1918, and quickly devastated the community. In a single week, 125 people, more than 5% of the town's population, perished from flu complications. By the time the pandemic waned the following March, 246 people had died, accounting to more than 10% of the population. This gave Silverton the dubious honor of having the highest mortality rate for the Spanish Flu in the entire nation. Lake Emma disaster On 4 June 1978, when the water from Lake Emma collapsed into Sunnyside mine, shooting out of a portal with a force that toppled a 20-ton locomotive. Fortunately, no injuries were reported as disaster occurred on a Sunday when nobody was present in the mine. Gold King Mine disaster In 2015, the EPA and its contractors caused an environmental catastrophe when they accidentally destroyed the plug holding water trapped inside the Gold King Mine, which caused three million US gallons (eleven thousand cubic meters) of mine waste water and tailings, to flow into a tributary of the Animas River. Demographics As of the census of 2000, there were 531 people, 255 households, and 149 families residing in the town. The population density was . There were 430 housing units at an average density of . The racial makeup of the town was 97.36% White, 0.75% Native American, 0.38% Pacific Islander, 0.75% from other races, and 0.75% from two or more races. Hispanic or