 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.