Pacific Coast Highway, known in Oregon as Oregon Coast Highway (U.S. 101).
The definitive West Coast highway.
Although Washingtonians do not seem to have an affectionate nickname for this Olympia–Los Angeles Highway, it is known as the Oregon Coast Highway, and as the Pacific Coast Highway. Its original southern terminal, per Droz, lay in San Ysidro, California.
Sources:
U.S. Highways
Don Wilson’s Highway 101 Project