The Six Area Codes Serving Colorado
Colorado runs on six area codes. Three of them, 303, 720, and 983, sit on top of each other across greater Denver and north-central Colorado. The 719 code holds the south and southeast on its own. The 970 code covers the north and west, now joined by the 748 overlay. Because overlays share territory, every local call in the state requires all 10 digits.
Two of the codes are young. The 983 code started serving the Denver region in June 2022, and 748 activated on July 7, 2025 for the 970 region. Neither changed any existing number. They exist only so carriers have fresh prefixes to hand out as the older codes fill up.
| Code | Region Covered | In Service | Overlay Status |
|---|---|---|---|
| 303 | Denver, Boulder, Aurora, Lakewood, Longmont, and nearby communities | 1947 | Original code, now overlaid by 720 and 983 |
| 720 | Same territory as 303 | 1998 | Overlay of 303 |
| 983 | Same territory as 303 and 720 | 2022 | Overlay of 303 and 720 |
| 719 | Colorado Springs, Pueblo, Alamosa, Trinidad, and the southeastern plains | 1988 | Standalone code from the 1988 split |
| 970 | Fort Collins, Greeley, Grand Junction, Durango, and the mountain corridor | 1995 | Split from 303, now overlaid by 748 |
| 748 | Same territory as 970 | 2025 | Overlay of 970 |
Colorado Area Code Coverage by Region
Think of the state as three numbering regions. Each one behaves as a single local calling identity, no matter how many codes it holds. State regulators and NANPA planning letters name the communities inside each region, so the boundaries are documented rather than guessed.
- 303 / 720 / 983 - greater Denver and north-central Colorado, including Aurora, Boulder, Brighton, Castle Rock, Englewood, Highlands Ranch, Lakewood, Littleton, Longmont, Thornton, Westminster, and Wheat Ridge
- 719 - southern and southeastern Colorado, including Colorado Springs, Pueblo, Canon City, Alamosa, Trinidad, La Junta, Lamar, Salida, Leadville, and Limon
- 970 / 748 - northern and western Colorado, including Fort Collins, Greeley, Loveland, Estes Park, Steamboat Springs, Vail, Breckenridge, Aspen, Glenwood Springs, Grand Junction, and Durango
Official coverage maps are published by the numbering administrator on the NANPA area code map resources page.
Those maps settle edge cases near regional boundaries, where a town's code is not obvious from distance alone. A prefix lookup there also confirms which rate center a number belongs to.
What Each Colorado Area Code Signals
Coloradans read identity into their codes. The 303 code is the original 1947 assignment and still carries strong local branding around Denver and Boulder. A 719 number signals southern Colorado: Colorado Springs, Pueblo, the San Luis Valley, and the southeastern plains towns. A 970 number points to northern Colorado, the ski towns, the mountain counties, and the Western Slope.
The overlays carry less romance. The 720 and 983 codes reflect Denver metro growth and overlay-era numbering rather than separate geography. And 748 is live but still culturally new, appearing only as 970 prefixes run out. None of that identity is reliable for screening calls, since numbers travel with their owners, but it explains why longtime residents guard an old 303 number.
Overlay or Split: Colorado Used Both
Colorado's map was drawn by both relief methods. Splits carved the state apart twice, when 719 took the south in 1988 and 970 took the north and west in 1995. People in the new regions had to change area codes. Every relief project since then has been an overlay: 720 in 1998, 983 in 2022, and 748 in 2025. Overlays leave existing numbers alone but force 10-digit dialing, because two neighbors can share a street while holding different codes.
- Split
- The old code keeps part of the territory and a new code takes the rest. Customers in the new region get a new area code.
- Overlay
- A new code is added on top of the same territory. Nobody's number changes, and 10-digit dialing becomes mandatory.
- Permissive Dialing
- A transition window when both the old and new dialing patterns still connect, ahead of a fixed cutover date.
NANPA's relief planning notes explain why regulators now prefer overlays. Nobody reprints letterhead, and no business loses a number it has advertised for decades.
Dialing Rule for Colorado Calls
Local calls take 10 digits everywhere in Colorado. The Denver overlay region has worked that way since the 720 era. The 719 and 970 regions converted later, and for a specific reason: 988 existed there as an ordinary exchange prefix, and the FCC's new crisis code could not share the pattern with 7-digit local numbers. Permissive dialing began April 24, 2021, and the FCC's ten-digit dialing guide documents the nationwide change behind it.
Important: Since October 24, 2021, 7-digit local calls no longer connect anywhere in Colorado. Dial the area code plus the number on every local call.
Toll calls may need 1 plus the 10 digits, and operator-assisted calls may use 0 plus 10, depending on the provider. NANPA's overlay planning for the 970 region lists all three patterns side by side, which makes it a handy reference when a call refuses to connect. The rest of the dialing landscape, from N11 shortcuts to star codes, lives on the Colorado phone codes page.
History of Colorado Area Codes
Colorado began as a one-code state. The 303 code arrived with the original North American plan in 1947 and covered everything from the plains to the Utah line. Four decades of growth ended that. Each later change tracked a wave of demand: Colorado Springs and the south first, then the fast-growing north and west, then Denver's metro boom, and finally the 988 conversion that standardized dialing statewide.
| Year | Event |
|---|---|
| 1947 | 303 implemented as Colorado's original statewide code |
| 1988 | 719 split off for southern and southeastern Colorado |
| 1995 | 970 split off for northern and western Colorado |
| 1998 | 720 overlaid 303 across the Denver region |
| 2021 | 719 and 970 moved to mandatory 10-digit local dialing for 988 |
| 2022 | 983 entered service as a second Denver-region overlay |
| 2025 | 748 entered service as the 970 overlay |
Assignment always runs ahead of service. NANPA's public NPA report shows 719 assigned on March 27, 1987 but in service March 5, 1988, and 970 assigned in September 1994 ahead of its April 1995 launch. The gap gives carriers and regulators time to prepare switches, signage, and customer notices. The two newest codes followed the same pattern: 983 was assigned in May 2021 for a 2022 launch, and 748 in December 2023 for its 2025 start.
Exchange Prefixes and Rate Centers
The three digits after the area code, called the NXX or central office code, tie a number to a rate center. Rate centers are billing and routing units, not city limits. Denver, Longmont, and Fort Lupton all appear as rate centers inside the 303 complex, while 719 spreads across centers like Colorado Springs, Pueblo, and Alamosa, and 970 covers everything from Fort Collins to Telluride. A single overlay region holds hundreds of prefixes across dozens of carriers.
The raw assignments are public. NANPA posts them as downloadable files on its central office code assignment records page.
The Colorado file sits in the Western-North region download, sorted by state and prefix. One caution applies: number portability lets a customer keep a number while switching carriers, so a prefix reveals its original assignee and rate center more reliably than the current provider.
Rate centers also stretch the meaning of a city name. Denver as a rate center reaches well past the municipal boundary, and one city can hold many prefix combinations thanks to overlays, wireless carriers, competitive local carriers, and internet phone providers. NANPA squeezes more life from each code through thousand-block pooling, which parcels prefixes out in blocks of a thousand numbers instead of ten thousand at a time.
The New 748 Area Code in Colorado
Colorado's newest code is still filling in. The Public Utilities Commission approved 748 as an all-services overlay of 970 in Proceeding No. 23V-0274T, decided November 20, 2023, and NANPA's Planning Letter 625 set the in-service date of July 7, 2025. New 748 prefixes are assigned only after the pool of available 970 prefixes runs out, so 748 numbers will surface gradually. State regulators told customers what to expect: anyone requesting new service, an added line, or moved service in the region may receive a 748 number, while existing customers keep their numbers and their 970 identity.
State involvement runs through the PUC's telecom program, described on the Colorado PUC telecommunications page.
NANPA forecasts exhaust and coordinates the industry work, but the commission makes the final call on every relief plan. No additional Colorado relief code beyond 748 is currently verified in NANPA's public reports, so the six-code map should hold for a while.
Verifying a Colorado Area Code
A quick check beats guessing when a caller ID shows an unfamiliar code. Confirm the code exists and see its territory in NANPA's references, then compare the claimed location against the coverage regions above. A caller who says Grand Junction while showing a 719 number deserves some doubt, though spoofing means even a matching code proves little on its own.
Note: Area code facts age quickly during relief planning, so treat NANPA's current reports as the tiebreaker whenever two sources disagree.