What is the oldest part of the Rocky Mountains?

The oldest part of the Rocky Mountains is the Canadian Rockies, specifically the section found in Alberta and British Columbia. These mountains were formed primarily during the late Precambrian to early Paleozoic eras, over 500 million years ago. The region features ancient rock formations, such as the Burgess Shale, which provide critical insights into early life on Earth. Overall, the complex geological history of the Rockies reflects a mix of tectonic activity and erosion over millions of years.