What was the greatest physical event in mesozoic era north America?

The *Laramide orogeny* was a major episode of mountain building that occurred in western North America during the Late Cretaceous through the Eocene epochs (80 million to 50 million years ago).

* The orogeny is named for Fort Laramie located where some important evidence for these ancient mountains is well exposed..

* Results:

a. Formation of Rocky Mountains

b. The *Sevier orogeny*, formed mountains that later eroded, depositing material that ultimately became the Colorado Plateau of today and other sedimentary basins of the Colorado Rockies and beyond (including the Uinta Formation).