Area Code 720 — Denver, Colorado

NANP area code

720

UTC−7, UTC−6 during daylight saving

State
Colorado
Primary city
Denver
Time zone
Mountain
In service
1998
Overlays
303, 983

The code reaches 72 communities and 13 counties across Colorado.

Was this call legitimate?

The area code itself carries no risk signal. 720 is assigned to Denver, Colorado, so a call from it is consistent with a real caller in that area — but the digits alone prove nothing, because they can be forged.

Caller ID is set by whoever places the call, not verified by the network. That is why neighbour spoofing works: an operation anywhere in the world can display a number that matches the area code — and often the first three digits after it — of the person being called, so the call looks local. Every community in the 720 territory is a plausible-looking origin for a forged 720 number, which is why one can be made to look like a neighbour to so many people. The same applies to its overlay codes 303 and 983, which serve the same ground.

If you did not recognise the call: let it go to voicemail — a legitimate caller with real business will leave one. Do not return the call using the number shown; look the organisation up independently and call the number you found. Never confirm personal details, card numbers, or one-time codes to someone who called you, however plausible the number looked.

Codes.zone publishes no complaint counts, risk scores, or caller identities. We hold no data on individual numbers and will not estimate what we cannot source.

Local time and when to call back

Time there now

Mountain · UTC−7, UTC−6 during daylight saving

Reasonable callback window

8:00 AM – 9:00 PM

local time in Mountain

Federal rules bar telemarketing calls to a residence outside 8:00 AM–9:00 PM in the called party's own time zone. It is a sensible bound for a personal callback too — and a caller who rang you well outside it was not observing it.

Overlay codes and ten-digit dialling

720 does not have its territory to itself. 303 and 983 cover the same ground, serving Denver and the rest of the 720 territory. An overlay is what a regulator adds when a region runs out of assignable numbers: rather than splitting the area and forcing half the residents to change their number, a second code is laid over the top and new numbers are issued from it.

The practical consequence: two neighbours on the same street can hold numbers in different area codes, so the code tells you nothing about which part of town a caller is in — and local calls must be dialled as all ten digits, because seven is no longer unambiguous.

Cities served

largest 20 by ZIP count
Communities served by area code 720, ranked by how many ZIP codes each holds.
CityZIP codesCounty
Denver66Adams County
Aurora17Adams County
Littleton16Arapahoe County
Boulder11Boulder County
Arvada7Jefferson County
Englewood7Arapahoe County
Broomfield4Boulder County
Golden4Jefferson County
Longmont4Boulder County
Westminster4Adams County
Brighton3Adams County
Castle Rock3Douglas County
Loveland3Larimer County
Commerce City2Adams County
Evergreen2Jefferson County
Parker2Douglas County
Wheat Ridge2Jefferson County
Allenspark1Boulder County
Bailey1Park County
Bennett1Adams County

52 further communities not listed. All Colorado area codes →

Each point is a community served by 720, plotted from its record coordinates. The outline is the convex envelope of those points — a footprint, not a boundary.
  • Reference points and footprint
  • Not an official NANPA boundary
  • Not a USPS delivery area

Scope every community matched to 720. Source geoinfo-dataset (full_dataset) ZIP→NPA (2018 snapshot), GeoNames US postal codes (2026-07 postal dump) and Census 2024 county Gazetteer (2024 Gazetteer). Updated . Coordinates are place reference points, not boundaries.

Counties

Prefixes inside 720

We do not publish the NXX prefixes inside 720. The assignment of prefixes to rate centres comes from LERG routing data, which is proprietary, and we will not estimate it from postal data — ZIP codes and telephone prefixes do not map onto each other. Awaiting a clean-rights NPA-NXX source.

Why this code exists

720 sits in the middle of its complex. It was added in 1998 over 303 (1947), and was later joined by 983 (2022) as the region kept running short of numbers.