Boulder, Colorado

Where Is Area Code 720?

Area code 720 is in north central Colorado. It serves the Denver metropolitan area and nearby communities along the Front Range. It is not limited to Boulder, even though Boulder is one of the cities in the area.

Area code 720 covers major cities such as Denver, Boulder, Aurora, Lakewood, Westminster, Longmont, Thornton, Arvada, and Centennial. It serves parts or all of counties in the Denver-Boulder region, including Denver County, Boulder County, Jefferson County, Adams County, Arapahoe County, and Broomfield.

The area includes well-known places such as downtown Denver, the University of Colorado Boulder, and Denver International Airport. It also sits near major geographic features such as the Rocky Mountain foothills and the South Platte River corridor.

History of Area Code 720

Area code 720 was created on June 1, 1998. The North American Numbering Plan added it as an overlay for area code 303, which is one of Colorado’s original area codes from 1947.

The overlay happened because the Denver-Boulder region needed more phone numbers. On September 1, 2022, area code 983 was added as another overlay for the same region. Since these are overlay codes, 10-digit dialing applies within the service area.

Key Facts About Area Code 720

• Area code 720 is in Colorado, and Boulder is one of the major cities in its service area.
• Area code 720 serves the same general region as area codes 303 and 983 in the Denver-Boulder metropolitan area.
• Area code 720 is in the Mountain Time Zone.
• Area code 720 is an overlay area code, not an original 1947 area code.
• Area code 720 was introduced on June 1, 1998, as an overlay to area code 303.
• Area code 983 began overlaying the same region on September 1, 2022.
• The service area includes major institutions such as the University of Colorado Boulder and major transportation hubs such as Denver International Airport.
• The 303, 720, and 983 area code region serves a large share of Colorado’s population in and around Denver and Boulder.

Frequently Asked Questions

What state is area code 720 in?

Area code 720 is in Colorado.

What major cities use area code 720?

Major cities that use area code 720 include Denver, Boulder, Aurora, Lakewood, Westminster, Longmont, Thornton, Arvada, and Centennial.

Is area code 720 a toll-free number?

No. Area code 720 is a geographic area code.