Why Denver Has Two Area Codes: 720 Explained

If a call from the 720 area code just showed up on your phone, you're hearing from the Denver metro area — but not from a different city than 303 covers. The 720 area code is one of Colorado's newer numbering codes, and unlike most area codes, it wasn't created to serve a new region at all — it exists purely to keep the Denver area supplied with fresh phone numbers.

This guide covers everything worth knowing about the 720 area code: where it's located, which cities and counties it covers, why it shares its territory with two other area codes, what time zone it runs on, the scam patterns to watch for, and how to get a local 720 number if you're opening a business or expanding into Colorado.

The 720 area code covers the Denver metro area in north-central Colorado, the exact same footprint served by 303. It's one of the most business-dense regions in the Mountain West, home to a growing mix of corporate headquarters, aerospace employers, and tech startups along Colorado's Front Range.

Major cities and communities in the 720 area code include:

• Denver: Colorado's capital and the largest city in the numbering plan area
• Aurora: one of the state's largest suburbs, stretching across three counties
• Lakewood and Arvada: major residential and commercial hubs west and northwest of Denver
• Boulder: home to the University of Colorado and a dense tech and biotech corridor
• Westminster, Centennial, and Broomfield: fast-growing suburbs anchoring the northern and southern metro

Because 720 is an overlay rather than a geographic code tied to a specific area, having a 720 number says nothing about which particular Denver suburb someone lives in — it's simply one of three area codes now issued across the same metro footprint.

Colorado's Denver-Boulder corridor grew so quickly through the second half of the 20th century that regulators had to intervene twice before 720 ever existed. On March 5, 1988, southeastern Colorado — including Colorado Springs and Pueblo — split off as area code 719. On April 2, 1995, the state's northern and western regions, including Fort Collins, Grand Junction, Vail, and Aspen, split off as area code 970, narrowing the original 303 area code to just the Denver metro.

Even that wasn't enough. Within just a few years, cell phones and pagers had exhausted the newly narrowed 303 supply, and on September 1, 1998, regulators introduced 720 as an overlay rather than splitting the metro a third time. It was Colorado's first overlay code, and it set the pattern that would later be repeated with 983 in 2022.

Colorado's Public Utilities Commission opted for an overlay specifically to avoid forcing existing 303 customers to change their numbers — a concern raised repeatedly during public comment periods on the state's numbering plans, according to filings with the Colorado Department of Regulatory Agencies. Instead, new phone lines in the region were simply assigned the new 720 code, while everyone with an existing 303 number kept it unchanged.

One practical side effect: because 720 shares its territory with 303 (and now 983), the region requires mandatory 10-digit dialing for every call — even between two neighbors in the same Denver zip code. If your business phone system still assumes 7-digit local dialing, this is worth double-checking.

The entire 720 area code sits in the Mountain Time Zone, observing:

• Mountain Standard Time (MST): UTC−7, in the winter months
• Mountain Daylight Time (MDT): UTC−6, from early March through early November

That means if you're calling a 720 number from the East Coast, you're generally two hours ahead — worth keeping in mind before you dial early in the morning or late in the evening.

Area code 720 itself is completely legitimate — it's simply one of three dialing codes assigned to a large, real part of Colorado. But like most active area codes, it's frequently spoofed by scammers who fake a local caller ID so residents are more likely to answer a call that looks like it's coming from their own neighborhood.

Common scams reported against 720 numbers include:

• Government impersonation: callers posing as the IRS, Social Security Administration, or a process server threatening legal action or claiming your identity was stolen
• One-ring (Wangiri) scams: a call rings once and disappears, hoping you'll call back a premium-rate number
• Fake utility shutoff threats: callers claim power or gas service will be cut off within hours unless an immediate payment is made
• Neighbor spoofing: scammers deliberately match the first six digits of your own number to appear more trustworthy

If you receive a suspicious call from a 720 number, don't share personal or financial information, hang up on any recorded message demanding immediate payment, and report the call to the Federal Trade Commission. The area code isn't the problem — caller ID spoofing simply makes it easy for bad actors to borrow it.

If you want a 720 number for personal or business use, the fastest option today is a cloud business phone platform. With a provider like Softtop, getting a 720 number takes just a few steps:

1. 1Sign up for a free trial — no credit card required
2. 2Open your number inventory and search Colorado → 720
3. 3Choose a local DID, toll-free number, or vanity number from Softtop's US inventory of 800+ area codes
4. 4Assign it to a team, an AI Receptionist, or an individual extension
5. 5Go live in minutes with unlimited US calling included

Because Softtop provisions numbers instantly and supports number porting with zero port-out fees, you can also move an existing 720 number onto the platform in five to ten business days if you're switching providers rather than starting fresh.

Beyond simple geography, a local 720 number gives a business real advantages when reaching customers across Denver, Boulder, and the Front Range — the same regional-trust dynamic that plays out for a 505 area code number one state over in New Mexico:

• Higher answer rates: people are more likely to pick up a call that looks local
• Regional trust: a familiar area code signals you're accessible and invested in the community
• Marketing consistency: a local number pairs naturally with localized ads, listings, and campaigns
• No physical office required: cloud phone systems let you serve the region without leasing space there

On Softtop, every 720 number is backed by the same tools used across the platform: an AI Receptionist that answers every call in under a second, full call recording and transcription, CRM sync with HubSpot and Salesforce, and 99.999% uptime backed by an SLA.

The 720 area code is a distinctive example of how phone numbering can grow without redrawing a single map line — Colorado's first overlay, introduced in 1998 to keep the Denver metro supplied with fresh numbers while every existing 303 customer kept their line unchanged. It runs on Mountain Time, shares its footprint with both 303 and 983, and requires 10-digit dialing like every overlay region nationwide.

Like any widely used area code, 720 is also a target for caller ID spoofing, so a little healthy skepticism toward unexpected calls goes a long way. And if your business wants to build a genuine local presence in the Denver metro, getting a number no longer requires a physical office or a new phone line — a cloud platform can have you calling, texting, and answering customers as a local business within minutes.

Whether you're trying to identify an unfamiliar call or planning your next market expansion, understanding the 720 area code — its geography, history, and quirks — puts you one step ahead.