U.S. Route 101 (US 101) is a United States Numbered Highway that runs along the West Coast from Los Angeles, California to Tumwater, Washington. Within the state of Washington, US 101 connects cities on the coast of the Pacific Ocean and encircles the Olympic Peninsula around the Olympic Mountains. It also serves as the main access for Olympic National Park, several state parks, and other scenic and recreational areas.

The Olympic Peninsula is a large arm of land in western Washington that lies across Puget Sound from Seattle, and contains Olympic National Park. It is bounded on the west by the Pacific Ocean, the north by the Strait of Juan de Fuca, and the east by Hood Canal. Cape Alava, the westernmost point in the contiguous United States, and Cape Flattery, the northwesternmost point, are on the peninsula. Comprising about 3,600 square miles (9,300 km2), the Olympic Peninsula contained many of the last unexplored places in the contiguous United States. It remained largely unmapped until Arthur Dodwell and Theodore Rixon mapped most of its topography and timber resources between 1898 and 1900.