North American Numbers Source-cited · ownership disclosed
Area code
406
In service
United States · since 1947

Montana (statewide)

Area code 406 is the single area code for the entire state of Montana, in place since the 1947 national numbering plan.

The essentials Numbering data · NumberResearch · as of 2026-09-18
Place
Montana (statewide)
Type
geographic
Status
in service
In service since
1947
Projected exhaust
2033 Q4

Status, dates and counts are read from NumberResearch (NANPA / CNAC / FCC records). Assignment records show initial assignees, not the carrier serving a number today.

A · Where it is

Where 406 is

All of Montana..

Communities served wholly or partly by 406:

BillingsMissoulaGreat FallsBozemanHelenaButte
B · Relationships

How it relates to other codes

The codes 406 was split from, spawned, or shares its area with. A split divides the map and changes some numbers; an overlay shares the same ground and changes none — what's the difference?

What's changing. Single statewide code, no overlay. Sufficient codes projected until 2031.
C · History

How 406 got here

1947
Established as Montana's sole area code under the original North American numbering plan.
Source: Wikipedia
2021-10-24
Ten-digit dialing adopted (988 hotline conflict resolution).
Source: Wikipedia
D · Capacity

How full it is

Prefixes assigned
768
Prefixes available
32
Thousands-blocks assigned
2,773

Prefix-assignment counts describe allocation to carriers, not how many individual numbers are in use. Full technical records: NumberResearch ↗.

Compare 406 with another code →
Sources
Wikipedia ↗
Area code 406
NumberResearch.org ↗
Live status, dates, assignment counts and exhaust forecast — data as of 2026-09-18 (CC BY 4.0).

Place, relationships and history above are compiled by North American Numbers from the sources listed and last checked 2026-09-18. A check date is not an expert review — see how this is made. Flag an error.