Area code 406

As of 2013, there were 1.7 million lines served by 47 carriers; all but two wireline providers support local number portability (the exceptions are small rural independents Hot Springs Telephone Company and Northern Telephone Cooperative).

Sufficient available codes for new exchanges in the 406 area code exist to meet anticipated demand until 2031; number pooling has been implemented in response to increased demand and inefficient use of 406 numbering resources.

In 2020, 988 was designated nationwide as a dialing code for the National Suicide Prevention Lifeline, which created a conflict for exchanges that permit seven-digit dialing.

This area code was therefore scheduled to transition to ten-digit dialing by October 24, 2021.

[3] The service area includes the following communities and their central office codes.