Norton Sound is an inlet of the Bering Sea on the western coast of the U.S. state of Alaska, south of the Seward Peninsula. It is about 240 km (150 mi) long and 200 km (125 mi) wide. The Yukon River delta forms a portion of the south shore and water from the Yukon influences this body of water. It is ice-free from June to October.Norton Sound was explored by Captain James Cook in September 1778.