Santa Clara County Route G8 is a 29.38 mile County Sign Route which is part of the San Francisco Bay Area transportation corridor. Santa Clara County Route G8 begins at California State Route 152 near the outskirts of Gilroy and terminates at former US Route 101 at 1st Street/Monterey Road near downtown San Jose. Santa Clara County Route G8 incorporates the notable Almaden Expressway and is historically tied to the New Almaden Quicksilver Mine.
(Santa Clara County Route G8 map image courtesy CAhighways.org)
Part 1; the history of Santa Clara County Route G8, the Almaden Road corridor and New Almaden Mine
The present corridor of Santa Clara County Route G8 ("G8") began to take shape with the emergence of the Almaden Expressway. According to the October 1960 California Highways & Public Works Unit 1 of the Almaden Expressway opened in November of 1959 between Alma Avenue near downtown San Jose south to the Guadalupe River as part of a Federal Highway Aid Secondary program. At the article publication date Unit 2 of the Almaden Expressway was being constructed over existing Almaden Road to the then new Hillsdale Expressway.
In 1845 Mexican Army Captain and trained geologist Andreas Castillero proved that the red rocks at Mine Hill contained Quicksilver (Mercury). Castillero filed a mining November 1845 with the Mexican Government for the "Santa Clara Mine." The earliest settlement at the Santa Clara Mine was Spanish Town which was plotted in late 1845. In 1846 Castillero sold some of his shares in the Santa Clara Mine to English investors of Barron, Forbes, & Company after being recalled by the Mexican Army due to the Mexican-American War. The new English investors renamed mine to "New Almaden" which was a reference to the Almaden Quicksilver Mine in Spain.
After the Mexican-American War the New Almaden Mine became part of what would become the State of California. The New Almaden Mine spiked in importance due to the onset of the California Gold Rush after the finding Gold at Sutter's Mill was announced. Mercury was an essential product used in the assay process for much of the mines of the California Gold Rush period and would ultimately see the New Almaden Mine become the largest producer in the world.
After the Mexican-American War the previous land claims of Alta California were evaluated via a Board of Commissioners. This board initially ruled in favor of honoring Andreas Castillero's mining claim during January of 1856 but the case eventually was elevated to the United States District Courts. The United States Supreme Court invalidated Castillero's mining claim during March of 1863. The Federal Government evaluated to nationalizing/purchasing the New Almaden Mine but backed off due to concerns of losing the loyalty of California during the American Civil War. Barron, Forbes, & Company sold the New Almaden Mine to American Investors from the Quicksilver Mining Company in 1864.
The Hacienda Reduction Works at the New Almaden Mine in an 1863 Carleton Watkins photo.
Spanish Town was joined by The Hacienda Settlement on Alamitos Creek by the early 1850s. The Casa Grande of The Hacienda Settlement was constructed by 1854 and still stands today. A third settlement known as Englishtown would develop at the New Almaden Mine in the 1860s. The corridor of Almaden Road became a well established and heavily traveled freight corridor from the New Almaden Mine north to San Jose. The New Almaden Mine and Almaden Road can be seen on the 1876 Thompson & West Santa Clara County Index.
Map 8 in the 1876 Thompson & West Santa Clara County Index shows the New Almaden Mine and Almaden Road greater detail.
Despite the bankruptcy of the Quicksilver Mining Company and decline of the New Almaden Mine it continued to operate through much of the 20th Century. Almaden Road was paved between 1920 through 1925. The New Almaden Mine began to be operated by several smaller mining operations which included the New Idria Mining Company beginning in 1928. Almaden Road can be seen as a major local maintained corridor on the 1935 Division of Highways Map of Santa Clara County. A underpass of the Southern Pacific Railroad mainline was constructed on Almaden Road in 1935.