 
Oregon, USA
43.10 N, 118.75 W 
    summit elevation 1435 m 
    Volcanic field 
Diamond Craters  volcano is located in SE Oregon,  11 km east of highway 205. The volcano covers and area of 60 sq km and consists of cinder cones and lava flows.
  
Further Reading
    Sherrod, D.R., Champion, D.E. and McGeehin, J.P., 2012. Age and duration of volcanic activity at Diamond Craters, southeastern Oregon. Journal of Volcanology and Geothermal Research, 247, pp.108-114.
Peterson, N.V. and Groh, E.A., 1964. Diamond Craters, Oregon. Ore Bin, 26(2), pp.17-34.
In the past 60,000  years.