Historical Towns (13) Eureka, Colorado History Click on an image to get more details or a direct link. Eureka Colorado ca 1900 Sunnyside Mill and Eureka Colorado 1929 View of Eureka, Colorado taken from the top of the Sunnyside Mill Young Mike O'Toole at a Hanson claim near Eureka, Colorado A prospector's claim tunnel entrance near Eureka, Colorado 1904 View of the Sunnyside Mill foundation from The Eureka Townsite Eureka Colorado 2009 Sunnyside Mill foundation and Eureka Townsite Sunnyside Mill foundation at Eureka Townsite School House Eureka Colorado Early view of Eureka, Colorado Eureka Colorado 1941 Eureka Colorado 1941