Within the heavily eroded volcanic deposits of the scenic John Day River basin is a well-preserved fossil record of plants and animals. This remarkably complete record, spanning more than 40 of the 65 million years of the Cenozoic Era (the "Age of Mammals and Flowering Plants") is world-renowned.
Authorized October 26, 1974, and established in 1975, this 14,000 acre park is divided into three widely separated units; the Sheep Rock Unit, Painted Hills Unit, and Clarno Unit. The monument's main headquarters is at the visitor center in the Sheep Rock Unit.