Boulder is a home rule city and the county seat of Boulder County, Colorado, United States. It is the largest city in Boulder County, with a population of 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 part of the Front Range Urban Corridor.
Pearl Street Mall in downtown Boulder
Boulder in 1900
Boulder's rock formations, the Flatirons
Autumn in Boulder
Boulder County is a county located in the U.S. state of Colorado of the United States. As of the 2020 census, the population was 330,758. The most populous municipality in the county and the county seat is Boulder.
Boulder County Courthouse
View of the eastern and southern borders of Boulder County and adjacent areas in Weld, Broomfield, and Jefferson counties, with north oriented to the left. The city of Boulder is near the lower border. Taken from the International Space Station on July 1, 2022.
Boulder and the mountains to the west of the city