Also in Southwest Alaska are the Pribilof Islands , Nunivak Island and other Bering Sea islands . There is a very large river delta made by the Yukon River and the Kuskokwim River . Southwest Alaska encompasses , roughly from west to east : the Pribilof Islands , Nunivak Island and other Bering Sea islands lying west of the Alaska coast and east of the Russian coast ; the immense combined delta of the Yukon River and Kuskokwim River ; hundreds of miles of interior highlands , including the lower and middle Kuskokwim drainages ; the entire watersheds of Goodnews Bay and Bristol Bay and other parts of the southern coast , including mountain ranges and great interior lakes including the Wood-Tikchik Lakes , Lake Iliamna , and Lake Clark ; the western heights of the Alaska Range , and its continuation southward as the Aleutian Range along the Alaska Peninsula and Aleutian Islands .