U.S. Route 101
U.S. Route 101, or U.S. Highway 101 (US 101) is a north–south United States Numbered Highway that runs through the states of California, Oregon, and Washington, on the West Coast of the United States. It is also known as (The Royal Road) where its route along the southern and central California coast approximates the old trail which linked the Spanish missions, pueblos, and presidios. It merges at some points with California State Route 1 (SR 1).
U.S. Route 101
Parts of Historic US 101 can still be found in San Diego County between Oceanside and the border with Mexico under a variety of different names. Through Oceanside it is called Coast Highway. In Carlsbad it becomes Carlsbad Boulevard, but to the south in Encinitas it is Coast Highway 101. Solana Beach keeps it consistent with Highway 101, but Del Mar changes it to Camino Del Mar. All of those together make up CR S21. From there it continues along Torrey Pines Road, La Jolla Village Dr and Gilman Dr to merge with I-5 in La Jolla. On I-5, it breaks away from the freeway to follow Mission Bay Dr (former I-5 bus.) before rejoining I-5. The old US 101 routing continues on I-5 in San Diego until Pacific Highway, the old US 101 freeway a little west of current I-5. It then continued on Harbor Drive and Broadway through Downtown San Diego and Chula Vista, then onto National City Boulevard in National City. As it returns to San Diego on its way to the Mexican border, it follows Beyer Blvd through Otay Mesa and then through other parts of San Diego near the border on east Beyer Blvd and east San Ysidro Blvd in San Ysidro. The southern parts of I-5 were US 101 for a period before I-5 was completed also. All have been decommissioned, but the roadways still exist and are occasionally signed as Historic 101.