The coldest state in the US is Alaska. It is the most northern US state.
Boston
Minnesota.
North Dakota
Alaska
maine
Alaska is a state, not a city. If you're asking if the coldest city in the US is in Alaska, then probably, depending on exactly how you define "coldest city". At any given moment, it's possible (if not terribly likely) that the coldest temperature measured in any US city is for a city not in Alaska.
San Fransisco, CA or Seattle, WA
Top part of Maine.
Alaska. In the continental United States, Minnesota takes the cake.
Minnesota, with an average temperature of 40.96 degrees Fahrenheit
Maine with an average temperature of 40.97 degrees Fahrenheit