The Billings Metropolitan Statistical Area is the largest metropolitan area in the U.S. state of Montana. Located in south central portion of the state, its population was 162,848 at the 2012 United States Census estimate. Consisting of Carbon and Yellowstone counties, it is the largest metropolitan area between Denver, Colorado and Calgary, Alberta Canada and between Spokane, Washington and Sioux Falls, South Dakota. It also has one of the largest trade, cultural, business and medical areas in the United States; this includes all of Montana, northern Wyoming and the western Dakotas. x200pxEnlargeDowntown Billings.