The U-S Environmental Protection Agency redesignated Billings as in compliance with federal air pollution standards.
Governor Steve Bullock says this is the first time EPA has reversed a non-attainment decision.
The EPA’s nonattainment designation was handed down in 2013. Federal officials pointed to the closure of the coal-fired Corette Power Plant as improving the air quality. But state officials disagree that’s the reason for the re-designation.