Coös County is a county in the U.S. state of New Hampshire, including the whole of the state’s northern panhandle. The county straddles two of the state’s tourism regions. The southernmost portion of the county is part of the White Mountains Region and is home to Mount Washington. The remainder of the county is known as the Great North Woods Region. Coös occupies the largest area of any New Hampshire county but has the smallest population: 33,055, as of 2010. It is the only New Hampshire county to have lost population between the 2000 and 2010 censuses. The county seat is Lancaster. Major industries are forestry and tourism, with the once-dominant paper-making industry in sharp decline. Coös County is part of the Berlin, NH–VT Micropolitan Statistical Area. It is the only New Hampshire county on the Canada-United States border, located adjacent to the Canadian province of Quebec.