Where did Triceritops live?

Triceratops fossils have been found in the US states of Montana, Wyoming, Colorado, and South Dakota and the Canadian provinces of Alberta and Saskatchewan, and date to between 68 and 65.5 million years ago. At that time the area was a subtropical, coastal floodplain with various river deltas. It was forested with plants such as conifers, cycads, ginkgoes, ferns, horsetails, and early angiOSperms such as primitive grasses and palm trees. Open areas would have had scattered trees and been covered in ferns. There were occasional peat swamps there, too. The region had distinct wet and dry seasons, and sometimes suffered from drought.