Route 60, from Oxnard via the coast to San Juan Capistrano, was extended from Oxnard to El Rio (midway to Ventura, now the site of the Oxnard Boulevard interchange with US 101), in 1925. At Point Mugu, a path for the highway was cut through the mountains using surplus World War I explosives, thus creating Mugu Rock. The 1921 legislation, in theory, made Route 60 a continuous coastal loop, with both ends at what became US 101 in Oxnard and at Capistrano Beach (since 1964 the southern terminus of SR 1 at Interstate 5 in Orange County). Route 56 was extended further south from Cambria to connect to present-day US 101 in San Luis Obispo in 1931.