The principal state highways in Coös County are New Hampshire Route 16, which runs mostly parallel to the Maine state line and through the city of Berlin, and New Hampshire Route 26, which traverses the Great North Woods from Vermont Route 102 southeast to Maine Route 26 towards Portland. The two major US Highways are US Route 2, which roughly bisects the county from Lancaster to the Oxford County line, and US Route 3, which runs from Carroll in the south to the Pittsburg–Chartierville Border Crossing, where it continues as Quebec Route 257.