The period of significance for the complex is from 1883, when Rasmus Hansen struck a rich body of ore and productive mining of the Sunnyside Extension Mine began, to 1910, when the Gold Prince Mill ceased operation. The complex has four important Areas of Significance – Archaeology, Engineering, Industry, and Transportation – and exhibits three property types: 1) Hard Rock Mine – Tunnel Mine; 2) Ore Concentration Facility – Concentration Mill; and 3) Mining Settlement and Residence – Worker Residence. This is filed under the Mining Industry in Colorado MPDF.