The Iditarod trail was a system of roadhouses and dog barns constructed every 20-30 miles to allow for travel without carrying weeks of provision, and was later famous for the Iditarod Trail Sled Dog Race. Over 65 tons of gold, equivalent to $2.5 billion today, were taken from the area using dog sleds, but demand for sled dogs decreased with the advent of airplanes during World War I.