1. Map showing distribution, composition, and age of early and middle Cenozoic volcanic centers in Idaho, Montana, west-central South Dakota, and Wyoming Yale Public content 1994. 2002-06-01T04:00:00Z. 2002-06-01T04:00:00Z. Geological Survey (U.S.). The Survey ; For sale by Map Distribution. English. Public. West (U.S.). Cenozoic.