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.

Longmont is a home rule municipality located in Boulder and Weld counties, Colorado, United States. Its population was 98,885 as of the 2020 U.S. Census. Longmont is located northeast of the county seat of Boulder. It is named after Longs Peak, a prominent mountain that is clearly visible from the city.