406 Area Code – Billings, Montana: Location, Time Zone & History

Montana is one of just eleven U.S. states served by a single area code, and 406 has covered its entire territory since 1947, when it was assigned as one of the original 86 area codes established by AT&T. Rather than splitting the state, as happened elsewhere, growth pressures over the decades have been managed through conservation measures. In 2021, ten-digit local dialing became mandatory statewide after the 988 central-office code was reserved nationally for the National Suicide Prevention Lifeline, which conflicted with existing 988 exchange numbers already in use within 406.

Facing a forecast exhaustion date of late 2027, the Montana Public Service Commission sought FCC relief in 2022, including individual telephone number pooling. NANPA later revised the projected exhaust date to the fourth quarter of 2028, and in 2025 the Montana PSC approved rate-center consolidation and other number-optimization strategies that pushed the projected exhaustion further out, to early 2033.

The code reaches communities across the state, including Billings, Missoula, Great Falls, Bozeman, Helena, Butte, and Kalispell, and touches an economy built on agriculture and ranching, tourism and outdoor recreation, mining, oil and gas, and a growing technology sector. Its single-code status has made 406 an informal symbol of Montana identity, with some residents marking April 6 as an unofficial "406 Day."