The North Slope Borough is the northernmost borough in the US state of Alaska and, thus, the northernmost county or equivalent of the United States as a whole. As of the 2020 census, the population was 11,031. The borough seat and largest city, comprising nearly 1/2 of the borough’s population, is Utqiaġvik, the northernmost settlement in the United St…The North Slope Borough is the northernmost borough in the US state of Alaska and, thus, the northernmost county or equivalent of the United States as a whole. As of the 2020 census, the population was 11,031. The borough seat and largest city, comprising nearly 1/2 of the borough’s population, is Utqiaġvik, the northernmost settlement in the United States.