Answer:
western North America
Step-by-step explanation:
The Cenozoic Era began 65 million years ago and lasts to the present. It means "new life" and is also known as the Age of Mammals. It is in this era that the current man, Homo Sapiens and technology emerges.
The Cenozoic Era is marked by widespread development on all continents, especially in low-lying plains, such as the Gulf and Atlantic coastal plains of North America. In addition, in that period Western North America was marked by being tectonically active.