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US area codes

Colorado area codes

A checked list of 6 in-service geographic area codes in Colorado, with their dates, overlay partners and dialing rules.

Last checked 14 October 2026

Area codes across North America

Codes in service in Colorado

Colorado has 6 geographic area codes in service: 303, 719, 720, 748, 970, 983. 303 is the oldest, dated 1947, and 748 the newest, dated 7 Jul 2025.1 All of Colorado's codes are on Mountain time.

Area codeNANPA locationNPA in-service dateIn-service overlay peersTime zoneLocal calls within the code
303CO1947720, 983Mountain10 digits
719CO5 Mar 1988None listedMountain10 digits
720CO1 Jun 1998303, 983Mountain10 digits
748CO7 Jul 2025970Mountain10 digits
970CO2 Apr 1995748Mountain10 digits
983CO17 Jun 2022303, 720Mountain10 digits

Scroll the table sideways to see every column. Sources: NANPA (14 October 2026 file).

History and overlays in Colorado

  • Before 1960: 303 (1947)
  • 1960 to 1989: 719 (5 Mar 1988)
  • 1990s: 970 (2 Apr 1995), 720 (1 Jun 1998)
  • 2020s: 983 (17 Jun 2022), 748 (7 Jul 2025)

Colorado's in-service overlay groups are 303/720/983; 748/970.1

  • 303/720/983: 303 (1947) was joined by 720 on 1 Jun 1998 and 983 on 17 Jun 2022.
  • 748/970: 970 (1995) was joined by 748 on 7 Jul 2025.

Dialing in Colorado

Local calls within a single area code in Colorado (303, 719, 720, 748, 970, 983) are all recorded as 10 digits. From any of Colorado's codes, local calls to another area code are all recorded as 10 digits.1

Neighbours of Colorado

Regions that border Colorado:

Rules that apply to every region are on the area-code reference.

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Further reading

Longer research pieces on this topic, each with its own source list and a downloadable PDF.

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Sources

Every regulatory and pricing claim on this page links to the primary source it came from. Figures were checked on the date shown at the top of the page; rules and prices change, so verify before relying on one.

  1. NANPA, NPA Database CSV, file dated 14 October 2026; US geographic codes, location, dates, overlay complexes, dialing plan and time zone. Retrieved 14 Oct 2026
    https://reports.nanpa.com/public/npa_report.csv

Keep reading

Reference
How overlays work
Why two codes can serve the same area and what ten-digit dialling changes.
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