The Northwest Territories, a portion of the old North-Western Territory, entered the Canadian Confederation on July 15, 1870. Since then, the territory has been divided four times to create new provinces and territories or enlarge existing ones. Its current borders date from April 1, 1999, when the territory's size was decreased again by the creation of a new territory of Nunavut to the east, via the "Nunavut Act" and the Nunavut Land Claims Agreement. While Nunavut is mostly Arctic tundra, the Northwest Territories has a slightly warmer climate and is both boreal forest (taiga) and tundra, and its most northern regions form part of the Canadian Arctic Archipelago.