The inlet was first explored by Europeans in 1778 when James Cook sailed into it while searching for the Northwest Passage. It was named after Cook in 1794 by George Vancouver, who had served under Cook in 1778.
The inlet stretches about 310 kilometers into Alaska from the Pacific Ocean. Its watershed covers about 100 000 square kilometers of southern Alaska, including the drainage areas of Mount McKinley and the Aleutian Range. Within the watershed ther are four active volcanoes and seven national parks. The city of Anchorage is located on the inlet, and about 400,000 people live within the Cook Inlet watershed.