San Miguel is located on the western bank of the Salinas River in Salinas Valley of northern San Luis Obispo County. Former US Route 101 before the present freeway was constructed was carried via Mission Street.
Part 1; the history of US Route 101 in San Miguel
The Salinas Valley was largely first explored by Europeans during the second Juan Bautista De Anza Expedition of Las Californias. In time the general route of the second De Anza Expedition became the path of El Camino Real ("The Royal Road"). The route of El Camino Real was intended to solidify a path of travel between the Catholic Missions of Las Californias. Mission San Miguel Arcangel was established on July 25th, 1797 on a site that was chosen on the Salinas River near a local Salinas Tribe. Each Mission was meant to be approximately 30 miles apart from each other which would require a single day of travel by horseback.
Following the advent of Mexican independence from Spain the usage of the term "El Camino Real" largely fell into disuse. Following the secularization of the Spanish Missions in August of 1833 the land holdings were split off into Ranchos. Despite El Camino Real functionally no longer existing it's path of travel remained a the favor way of traversing Alta California. During the American period Mission San Miguel Arcangel was returned to the Catholic Church in 1859. The Catholic Church subsequently reopened Mission San Miguel Arcangel in 1878. San Miguel's profile was further raised in the 1880s when the Southern Pacific Railroad built a line through Salinas Valley. Indeed San Miguel can be seen as a stop on the Southern Pacific Railroad on the the 1890 George F. Cram Railroad Map of California.
The era of State Highway Maintenance through San Miguel would ultimately begin with the 1909 First State Highway Bond Act which was approved by voters in 1910. One of the highways approved through the 1909 First State Highway Bond Act was a 481.8 mile highway originating at the City Limits of San Francisco which terminated in San Diego. This highway would ultimately come to be known in time as Legislative Route Number 2 ("LRN 2").
San Miguel was ultimately part of the American El Camino Real which began being signed as an Auto Trail starting in 1906. Early LRN 2 and the American El Camino Real can be seen on what is now Mission Street in San Miguel on the 1917 California State Automobile Association Map.
US 101/LRN 2 through San Miguel can be seen in detail on the 1935 Division of Highways Map of San Luis Obispo County.
The March/April 1958 California Highways & Public Works features the San Miguel Bypass. The San Miguel Bypass is stated to be a 3.1 mile long realignment of US 101 south of San Miguel north to the southern boundary of Camp Roberts. The San Miguel Bypass opened to traffic as the new alignment of US 101 in late November 1957.
Part 2; a drive on former US Route 101 in San Miguel via Mission Street
From modern US 101 one can access Mission Street via Exit 241A.
Mission Street from Exit 241A heads southward into downtown San Miguel. Access back to modern US 101 can be found at 10th Street.
South of 10th Street the alignment of Mission Street passes by Mission San Miguel Arcangel.