The U.S. state with the most extensive part of the Rocky Mountains is Colorado.

Colorado contains the highest peaks of the Rocky Mountains, including Mount Elbert, which is the tallest mountain in the contiguous United States the state is home to several significant national parks, such as Rocky Mountain National Park, which showcases the stunning landscapes and diverse ecosystems of the Rockies. While other states like Montana and Wyoming also have significant portions of the Rockies, Colorado encompasses the most extensive and prominent sections of the range, making it a focal point for the Rocky Mountains.