Area Code 720: Complete Guide to Denver-Area Coverage, Cities, and Dialing

Area code 720 serves the Denver metropolitan area in Colorado. Implemented on June 1, 1998 as an overlay to the original 303 area code, it addresses the growing demand for telephone numbers driven by population growth and the proliferation of mobile phones and pagers. The 720/303 overlay complex now includes a third area code (983, activated June 17, 2022), providing approximately 23.8 million phone numbers for a population of about 3.5 million people in the region. As of 2024, approximately 96.1% of available prefixes have been assigned, with 769 active prefixes serving the area. This guide covers everything you need to know about the 720 area code: geographic coverage, major cities served, dialing patterns, regulatory oversight, telecommunication services, and helpful resources.

Where is Area Code 720 Located?

Area code 720 serves the north-central region of Colorado, overlaying the existing area code 303. Both area codes cover the same geographic area, requiring 10-digit dialing for all calls within the region. This overlay system, implemented in 1998, addressed the increasing demand for phone numbers from the Denver area's rapid population growth. The numbering plan area (NPA) comprises Denver and Boulder, as well as their surrounding suburbs, including Lakewood, Littleton, Longmont, Broomfield, Aurora, and Castle Rock.

What Cities Are in the 720 Area Code?

Area code 720 covers 25 cities and 10 counties across Colorado's Front Range. The most prominent cities include:

• Denver: As the state capital and largest city with a population of 715,522 (2020 Census), Denver anchors the 720 area code for businesses and residents. The city accounts for 18.5% of the overlay area's total population.
• Aurora: With 386,261 residents, Aurora represents a significant portion of the area's population and telecommunication activity (10.0% of total).
• Lakewood: Another large suburb serving the western metro area with substantial residential and commercial telecommunications needs.
• Arvada: With 124,402 residents (3.2% of total), Arvada occupies a central location within the Denver metropolitan area.
• Boulder: Known for its vibrant university and tech scene with 330,758 county residents, Boulder highlights the region's diverse economic landscape.
• Thornton: A major northern suburb with 141,867 residents (3.7% of total).
• Centennial: A rapidly growing city south of Denver, exemplifying the ongoing development within the 720 service area.
• Longmont: Serving 98,885 residents in the northern part of the coverage area.

Complete County Coverage: Area code 720 covers ten counties: Denver, Jefferson, Arapahoe, Weld, Adams, Boulder, Douglas, Clear Creek, Gilpin, and Larimer. Together, these counties represent a total Census 2020 population of 3,865,062 people.

The 720/303/983 overlay also includes smaller communities such as Littleton, Brighton, Englewood, Golden, Westminster, Wheat Ridge, Erie, Highlands Ranch, Castle Rock, and Columbine, along with mountain communities like Evergreen, Idaho Springs, and Allenspark.

Similar area code overlays exist in other major metropolitan areas, such as area code 201 in New Jersey and area code 202 in Washington DC.

How to Dial Area Code 720: A Practical Guide

The 720/303/983 overlay requires specific dialing patterns to ensure successful call completion. Here's what you need to know:

Standard Dialing Requirements

Local Calls within the Overlay Area:

• Required Format: 10 digits (area code + 7-digit number)
• Example: To call 720-555-1234, dial exactly those 10 digits
• Important: Do NOT dial "1" before the area code for local calls
• Applies to: All calls within Denver, Boulder, Aurora, and surrounding communities

Long-Distance Calls:

• Within Colorado (outside 720/303/983 area): 1 + 10 digits
• Example: Calling Colorado Springs (719 area code): 1-719-555-1234
• Outside Colorado: 1 + 10 digits

Operator-Assisted Calls: 0 + 10 digits

Emergency and Special Services:

• Emergency: 911 (3 digits only – works in all overlay areas)
• Other Services: 211, 311, 411, 511, 611, 711, or 811 (if available in your community)
• National Suicide Prevention Lifeline: 988 (activated July 16, 2022)

Technical Terms Explained

• HNPA (Home Numbering Plan Area): The area code region where your phone number is registered (in this case, 720/303/983)
• FNPA (Foreign Numbering Plan Area): Any area code region outside your home area
• Permissive Dialing: A grace period after an area code change when both old and new dialing patterns work. This period has ended for the 720/303 overlay – 10-digit dialing is now mandatory.

Common Dialing Scenarios

Scenario 1: Calling from a 720 number to a 303 number in Denver

• Action: Dial all 10 digits (303-555-xxxx)
• No "1" prefix needed

Scenario 2: Calling from Denver (720) to Colorado Springs (719)

• Action: Dial 1 + 719-555-xxxx
• This is a long-distance call requiring "1"

Scenario 3: Calling from outside Colorado to a 720 number

• Action: Dial 1 + 720-555-xxxx

Troubleshooting Call Connection Issues:

If your call doesn't connect:

1. Verify you're dialing exactly 10 digits for local calls (no "1" prefix)
2. Confirm you're including the area code (720, 303, or 983)
3. For long-distance calls, ensure you're dialing "1" first
4. Update any speed dial or contact list entries to 10-digit format
5. Check that your phone system or PBX recognizes 983 as a valid area code
6. If issues persist, contact your telecommunications provider

Equipment Updates Required: Ensure all devices recognize 10-digit dialing and the 983 area code: cordless phones, PBX systems, fax machines, alarm systems, medical alert devices, gate systems, and contact lists.

Geographic Coordinates: Pinpointing Arvada

Arvada's geographic coordinates are:

• Latitude: 39.80276
• Longitude: -105.08748

These coordinates place Arvada near the center of the Denver metropolitan area, reflecting its central role within the 720 area code. Use these coordinates for mapping and location-based services. Other major city coordinates in the 720 area include Denver (39.7392° N, 104.9903° W) and Boulder (40.0150° N, 105.2705° W).

Regulatory Information: Navigating the Telecom Landscape

Area code 720, like all North American area codes, falls under the jurisdiction of the North American Numbering Plan Administration (NANPA). NANPA manages the allocation of area codes and phone number resources. The Colorado Public Utilities Commission (PUC) regulates telecommunications services within the state, including oversight of area code implementations and consumer protection.

Number Portability Rights

Under FCC regulations, you have the right to keep your phone number when changing service providers within the same geographic area:

Key Portability Facts:

• Port your 720 number between wireline, wireless, and VoIP providers
• Process timeline: Simple ports (single line) complete within one business day
• Your rights: Carriers cannot refuse to port your number, even if you owe money for outstanding balances or early termination fees
• Important: Do NOT cancel service with your old provider before initiating service with the new provider
• Fees: Providers may charge porting fees, but you can often negotiate or waive these

How to Port Your Number:

1. Contact your new service provider to start the porting process
2. Provide your current 10-digit phone number
3. Provide account information from your current provider (account number, PIN)
4. Wait for the port to complete (typically 1 business day for wireless-to-wireless)
5. Your old service automatically terminates once the port completes

Consumer Protection Resources:

• Report telecommunications issues to the Colorado PUC
• File complaints with the FCC Consumer Complaint Center
• Register your number with the National Do Not Call Registry to reduce telemarketing calls
• Report phone scams to the FCC's scam reporting page

Telecommunications Services: Connecting Colorado

Area code 720 supports a wide range of telecommunications services for residential and business needs. The overlay structure with area codes 303 and 983 ensures sufficient number availability for the region's growing population and expanding businesses, with approximately 23.8 million phone numbers available across the three-code overlay complex.

Service Types Available

Landline Services: Traditional wireline telephone service from carriers including CenturyLink (formerly Qwest) and other local providers. As of 2024, approximately 60.7% of active 720 prefixes support landline use.

Wireless Services: Mobile phone service from major carriers and regional providers. Approximately 39.3% of active prefixes support wireless use, though number portability allows any number to function as wireless.

VoIP (Voice over Internet Protocol) Services: Virtual phone numbers and internet-based calling from providers including:

• National VoIP providers (RingCentral, Vonage, 8x8, Nextiva)
• Regional and specialized providers (VoIPstudio, Dialpad, Ooma)
• Business-focused platforms with 720 number availability

VoIP Advantages for 720 Numbers:

• Establish a local 720 presence without physical location in Denver
• Use 720 numbers on multiple devices simultaneously
• Access advanced features (call routing, voicemail-to-email, analytics)
• Pay lower costs compared to traditional landlines
• Port existing 720 landline or wireless numbers

Carrier Services: Choosing the Right Provider

Major telecommunications carriers serving area code 720 include:

Wireline/Landline Providers:

• CenturyLink (formerly Qwest Corp): Primary incumbent local exchange carrier (ILEC) for the region
• Comcast/Xfinity: Cable-based phone service bundled with internet and TV
• Other local providers: Various competitive local exchange carriers (CLECs)

Wireless Carriers:

• National carriers: Verizon, AT&T, T-Mobile, Sprint (now part of T-Mobile)
• Regional carriers: U.S. Cellular and others
• MVNOs (Mobile Virtual Network Operators): Mint Mobile, Cricket Wireless, Metro by T-Mobile, Boost Mobile, Visible, Google Fi, and others offering lower-cost plans using major carrier networks

Selection Criteria for Choosing a Provider:

• Network coverage quality in your specific Denver-area location
• Data speeds and reliability (especially for 5G service)
• Customer service ratings and support availability
• Pricing structures and contract requirements
• Features included (mobile hotspot, international calling, etc.)
• Business-specific needs (multi-line discounts, unified communications)

Infrastructure Notes:

• Major carriers actively deploy 5G wireless service throughout the Denver metro area
• Fiber optic broadband infrastructure expands continuously, particularly in Denver proper and surrounding suburbs
• Rural and mountain areas within the 720 coverage zone may have limited high-speed options

Additional Resources: Expanding Your Knowledge

For further information on area codes, telecommunications regulations, and related topics, explore these resources:

Federal & State Regulatory:

• Federal Communications Commission (FCC): Regulates interstate and international communications, consumer protection, and telecommunications policy
• North American Numbering Plan Administration (NANPA): Official area code administrator with detailed NPA information
• Colorado Public Utilities Commission: State-level telecommunications regulation and consumer resources

Local & Economic Development:

• Metro Denver Economic Development Corporation: Insights into Denver's economic landscape and infrastructure

Consumer Tools:

• National Do Not Call Registry: Register to reduce unwanted telemarketing calls
• FCC Consumer Complaint Center: File complaints about telecommunications services
• Phone Lookup Tools: WhitePages.com, TrueCaller, or carrier-specific reverse lookup services
• Carrier Comparison Sites: WhistleOut, BestPhonePlans, Coverage Mapper

For more information on phone number formats and standards, see our guide on E.164 phone number formatting.

Frequently Asked Questions About Area Code 720

What cities are in the 720 area code?

Area code 720 serves major Colorado cities including Denver, Aurora, Arvada, Lakewood, Boulder, Thornton, and Centennial. The 720 area code covers 25 cities total throughout the Denver metropolitan area and overlays with area codes 303 and 983, serving the same geographic region across multiple counties: Denver, Arapahoe, Jefferson, Adams, Boulder, Weld, Douglas, Clear Creek, Gilpin, and Larimer counties.

Is area code 720 the same as 303?

Yes, area code 720 and 303 serve the same geographic area in Colorado. Area code 720 was introduced on June 1, 1998 as an overlay to area code 303 to accommodate the growing demand for phone numbers in the Denver metropolitan area from population growth and mobile device proliferation. A third overlay, 983, was added on June 17, 2022. All three area codes (303, 720, and 983) cover identical territories, requiring 10-digit dialing for all calls within the region.

Do I need to dial 1 before calling a 720 number?

For local calls within the 720/303/983 overlay area, dial all 10 digits (area code + 7-digit number) WITHOUT the "1" prefix. For calls from outside Colorado or when calling other Colorado areas outside the 720/303/983 region (such as Colorado Springs with 719), dial 1 + 10 digits. Always use 10-digit dialing for local calls in the Denver metro area. FCC regulations mandate 10-digit dialing in overlay areas.

When was area code 720 introduced?

Area code 720 was officially implemented on June 1, 1998 as an overlay to the existing area code 303. The implementation process involved a transition period where consumers and businesses updated their dialing habits and equipment to accommodate mandatory 10-digit dialing. This overlay system was designed to address the rapid population growth and increasing demand for phone numbers in the Denver metropolitan area, driven by the proliferation of cell phones, pagers, fax machines, and internet dial-up connections. The Colorado Public Utilities Commission oversaw the implementation with public notification campaigns to educate residents about the change.

Can I get a 720 phone number for my business?

Yes, you can obtain a 720 phone number for your business through various telecommunications carriers operating in the Denver area. Options include:

Traditional Carriers:

• CenturyLink, Comcast, and other wireline providers for landline service
• Verizon, AT&T, T-Mobile for wireless business lines

VoIP Providers (Popular for Businesses):

• National providers like RingCentral, Nextiva, 8x8, Vonage
• Specialized business VoIP services like Dialpad, Ooma Office, Grasshopper

Steps to Obtain a 720 Number:

1. Research and compare carriers based on your business needs
2. Contact your preferred provider to request a 720 area code number
3. Provide business information and select service plan
4. Choose from available 720 numbers (some providers allow number selection)
5. Set up service (typically 1–3 business days for activation)

Cost Considerations: Basic business lines range from $20–50/month for traditional service, while VoIP options may range from $15–40/user/month depending on features. Number acquisition may incur one-time setup fees ($0–50 typically).

What is the time zone for area code 720?

Area code 720 operates in the Mountain Time Zone (MT), which is UTC-7 during Mountain Standard Time (MST) and UTC-6 during Mountain Daylight Time (MDT). Colorado observes daylight saving time, with clocks moving forward one hour in March and back one hour in November. This applies to all cities and communities within the 720 area code, including Denver, Aurora, Boulder, and surrounding areas in Colorado.

How do I block spam calls from 720 numbers?

Block spam calls from 720 numbers using these methods:

Built-in Phone Features:

• iPhone: Settings > Phone > Silence Unknown Callers
• Android: Phone app > Settings > Blocked numbers

Carrier-Provided Services:

• AT&T Call Protect, T-Mobile Scam Shield, Verizon Call Filter
• Most major carriers offer free basic spam detection with premium options

Third-Party Apps:

• RoboKiller, Truecaller, Nomorobo, Hiya
• These apps use crowdsourced databases to identify and block spam

Government Registry:

• Register at donotcall.gov (National Do Not Call Registry)
• Reduces legitimate telemarketing but doesn't stop illegal scam calls

Report Scams:

• File complaints with the FCC for illegal robocalls
• Report to the Colorado Attorney General for state-level enforcement

Is area code 720 toll-free?

No, area code 720 is not a toll-free number. It's a standard geographic area code for the Denver metropolitan area in Colorado. Toll-free area codes include 800, 888, 877, 866, 855, 844, and 833. Calls to 720 numbers are charged according to your phone plan's local or long-distance rates. Within the 720/303/983 overlay area, local calls are typically included in unlimited calling plans, but long-distance charges may apply when calling from outside the region depending on your service plan.

What counties does area code 720 cover?

Area code 720 covers ten counties in Colorado: Denver County, Jefferson County, Arapahoe County, Weld County, Adams County, Boulder County, Douglas County, Clear Creek County, Gilpin County, and Larimer County (partial). This includes the Front Range urban corridor and extends throughout the north-central region of Colorado, encompassing both major cities and smaller communities within these county boundaries. The total population served is approximately 3.87 million people according to the 2020 Census.

How can I verify if a 720 number is legitimate?

Verify a 720 number's legitimacy using these methods:

Reverse Lookup Services:

• Free options: WhitePages.com, TrueCaller, 411.com
• Paid services: BeenVerified, Spokeo, Intelius (more detailed information)

Search Engines:

• Google the number in quotes: "720-555-1234"
• Check for reported scams or business listings

Red Flags to Watch For:

• Unsolicited calls requesting personal information or payment
• Pressure tactics demanding immediate action
• Requests for gift cards, wire transfers, or cryptocurrency
• Calls claiming to be from government agencies threatening arrest
• Robocalls with pre-recorded messages

Verification Steps:

• Call back during business hours to verify identity
• Check the business's official website for listed contact numbers
• Contact the company directly using a number from their official website
• Request callback from a supervisor or verified number

Reporting Suspicious Activity:

• Colorado Public Utilities Commission
• FCC Consumer Complaint Center
• Federal Trade Commission for scams

What happens if the 720 area code runs out of numbers?

As of 2024, area code 720 (along with overlays 303 and 983) has 23.8 million available phone numbers serving approximately 3.5 million people. Current data shows 96.1% of 720 prefixes are assigned, but the addition of 983 in 2022 relieved immediate exhaustion concerns. If number exhaustion becomes imminent again, NANPA and the Colorado PUC would implement another overlay area code. No further relief planning is currently underway, indicating sufficient number capacity for the foreseeable future.

Summary: Everything You Need to Know About Area Code 720

Area code 720 serves as a critical telecommunications identifier for the Denver metropolitan area in Colorado. This overlay area code, implemented on June 1, 1998, alongside area code 303 (and joined by 983 in 2022), covers major cities including Denver, Aurora, Arvada, Lakewood, Boulder, Thornton, and Centennial across ten counties.

Key Points:

• Geographic Coverage: Serves 25 cities and 10 counties in north-central Colorado's Front Range urban corridor
• Population Served: Approximately 3.87 million people (2020 Census)
• Overlay System: Shares territory with area codes 303 and 983, requiring 10-digit dialing for all local calls
• Number Capacity: 23.8 million phone numbers available across the three-code overlay; 96.1% of 720 prefixes currently assigned
• Major Cities: Includes state capital Denver (715,522 pop.) plus Aurora (386,261), Boulder County (330,758), and other growing communities
• Time Zone: Mountain Time (MT) – UTC-7 standard, UTC-6 daylight saving
• Regulation: Overseen by NANPA and Colorado Public Utilities Commission
• Implementation: Area code 720 introduced June 1, 1998; area code 983 added June 17, 2022
• Service Mix: 60.7% landline prefixes, 39.3% wireless prefixes (though portability allows flexible use)

Next Steps to Explore:

1. Research Local Carriers: Compare service plans from CenturyLink, Comcast, wireless carriers, and VoIP providers to find the best 720 phone number solution for your residential or business needs
2. Understand 10-Digit Dialing: Practice the mandatory 10-digit dialing format (area code + 7 digits, no "1" prefix for local calls) to ensure seamless communication within the Denver metro area
3. Explore Business Phone Options: Investigate VoIP solutions and virtual phone systems that offer 720 area code numbers for establishing local presence in Colorado without physical location requirements
4. Review Spam Protection: Set up call blocking features through your carrier or third-party apps and register with the National Do Not Call Registry at donotcall.gov
5. Check Regulatory Compliance: Visit the Colorado PUC website at puc.colorado.gov to understand telecommunications regulations affecting your 720 area code services
6. Understand Number Portability: Research your rights under FCC regulations to transfer phone numbers between carriers (typically completed in one business day for simple ports)
7. Optimize Business Listings: Ensure your 720 phone number is correctly listed in online directories and business profiles for maximum visibility
8. Update Equipment: Verify that all phone systems, PBX equipment, alarm systems, and stored contacts recognize 10-digit dialing and the 983 area code

Conclusion: Mastering Area Code 720

Area code 720 is a vital component of Colorado's telecommunications network serving the Denver metropolitan area. Understanding its coverage (25 cities across 10 counties), dialing patterns (mandatory 10-digit local dialing), regulatory framework (NANPA and Colorado PUC oversight), and available services (landline, wireless, and VoIP options) helps you navigate the local telecom environment effectively.

The overlay system with 303 and 983 provides sufficient capacity with 23.8 million available numbers for continued regional growth. Whether you're a resident, a business owner, or visiting the area, this guide equips you with the knowledge to communicate seamlessly within the 720 area code. Remember: the 720/303/983 overlay requires 10-digit dialing for all local calls without the "1" prefix – essential for successful communication in the Denver metropolitan area. As the region continues to grow, understanding area code 720 and your consumer rights (including number portability and spam protection) becomes increasingly important for staying connected in Colorado's dynamic Front Range corridor.