The City of Boulder is a home rule municipality that is the county seat and most populous municipality of Boulder County, Colorado, United States. The city population was 108,250 at the 2020 United States Census, making it the 12th most populous city in Colorado. Boulder is the principal city of the Boulder, CO Metropolitan Statistical Area and an important part of the Front Range Urban Corridor.
Boulder is located at the base of the foothills of the Rocky Mountains, at an elevation of 5,430 feet (1,655 m) above sea level. Boulder is 25 miles (40 km) northwest of the Colorado State Capitol in Denver. It is home of the main campus of the University of Colorado, the state's largest university.