Area code 303 serves the north-central part of Colorado, primarily the Denver metro area. It was one of the first area codes and is now overlaid by 720 and 983 due to regional growth. In the heart of this zone is Boulder, a city known for its stunning Flatirons backdrop, outdoor recreation, and progressive community. Pearl Street Mall, local breweries, and the University of Colorado Boulder are defining features of this environmentally conscious and lively city.