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McLaughlin Natural Reserve



The discovery of silver in nearby Napa Valley attracted prospectors to the Morgan Valley - Knoxville area in 1858-1859. No silver was found, but in 1861 mercury ("quicksilver") in its cinnabar form was discovered. Mercury ore was then extremely valuable because it was used in the gold recovery process known as amalgamation. Several mines went into operation, beginning with the XLCR (pronounced Excelsior) in 1861 and the Manhattan in 1869. The XLCR, later renamed the Redington, Boston and finally Knoxville mine, became perhaps the state's third largest mercury mine after the legendary New Idria and New Almaden mines.

William Brewer, whose accounts of traveling up and down California in 1861-1865 on the state's first geologic survey are a naturalists' classic, never visited the Knoxville mine, but his description of conditions faced by mercury miners at New Idria are probably representative of what took place at Knoxville. Miners worked in deep shafts, often under extremely hot conditions because of the geothermal activity associated with mercury deposits. The worst health effects were suffered by the workers who cleaned the crude furnaces used to roast the mercury out of the ore. Brewer describes these workers being paid the then-exorbitant wage of $20 a day to ruin their health for a lifetime. In a more amusing account of a visit to the Knoxville mine, taken from an 1872 article in the Napa Reporter, the journalist survived a steamy and sulfurous descent to a depth of 220 feet, and described what is now the McLaughlin Reserve as "a terrible waste of God's country... being nothing but a jumble of hills and canyons covered with sage brush."2

By 1880 the town of Knoxville had about 300 people and fifty buildings, including a hotel, church and school. Most of the inhabitants were immigrant men between the ages of 25 and 35. The prosperity of the town fluctuated with the market value of mercury, and when the price hit bottom in 1910, the town diminished to five dwellings. Mining activity resumed during wartime (1915-1918, 1939-1943) when the price of mercury soared due to its use in explosive detonators.

Gold in the form of microscopic flecks and tiny veins is associated with the same hot springs formations that host mercury. On July 26, 1875, US Deputy Mineral Surveyor Frederick Mow discovered gold in the Knoxville area. However, the gold deposit at McLaughlin was not economical to exploit until the 1970's, when the recognition of microscopic gold deposits, technological advances in mining methods, and high gold prices all coincided.

The Knoxville town and mine site was cleaned up in 1984 by a contractor working for the Gamble family, who then owned the land. The old furnaces and piles of roasted ore (calcine) were buried and the buildings were leveled. In 1992, Homestake bought the Gamble ranch, and a lot-line adjustment added Knoxville to the future McLaughlin Reserve. The town is now reduced to a few stone walls, and the mine is visible as a cliff of orange-colored rock; the tunnels are long since covered up. Oaks are noticeably sparse around the Knoxville site. This may be a legacy of mining, since one and a half cords of wood were needed to fire the mine furnaces for 24 hours. However, the Gambles also cleared oaks in this area in the 1960's in an attempt to improve the range for cattle.

Manhattan Mine

Manhattan Mine, 1881

Another historic mine, the Manhattan, was operated through the 1970's by William Wilder of the One Shot Mining Company. After mercury mining became unprofitable, Wilder managed to keep his business going by mining decorative stone from the old hot springs terrace and recycling mercury batteries. Wilder had an office in several 1959 San Francisco city buses, and had a knack for all things mechanical. When he sold his land to Homestake in 1981, Wilder moved the old Manhattan mine equipment and the rest of his "boneyard", including the buses, to a parcel along the Reiff Road where it can still be seen. The mine site itself cannot be seen, since it is now Homestake's open pit.

Four old mines above Davis Creek were consolidated into the Reed mine, the remains of which can be seen above the Reiff Road where Davis Creek enters the reservoir. The Reed mine has been the major focus of mercury cleanup and research efforts sponsored by Homestake, which are described in the aquatic ecology chapter. The Harrison mine, also in the Davis Creek watershed, sits abandoned on a private inholding within the reserve. Also on this land is the residence of the Stroop family, descendants of the Harrisons who filed the 1867 mine claim. Remains of the original Harrison homestead can be seen on a knoll just south of the mine and north of Knoxville-Berryessa Road.

The late nineteenth century also brought a wave of homesteaders who grew crops and raised livestock in Morgan Valley. The Morrell/Hand ranch occupied a site that was previously a Native American settlement and later became the site of Homestake's Core Shed, where the company stored its exploration drill core and created its company picnic area. The large black walnut trees at this site date to 1863, the same year the homestead papers were filed; botanists debate whether these trees are of Californian or East Coast stock. Also present at the Core Shed are pears, pomegranates and other old introduced trees. The large flat field just north of the Core Shed was irrigated and used to grow hay. In the former Quarry Valley, where the tailings pond now lies, was the large homestead of the Ebbinghausen family. Other homesteads were found at Springer's Flat, a mile southeast of Morgan Valley; and at the a site just west of the waste rock pile, where old vineyards can still be seen.

As elsewhere in the west, more homesteaders failed than succeeded in the arid landscape. By the early twentieth century, only a few ranchers and miners lived in Morgan Valley. The 1960s and 1970s brought additional settlers, seeking to escape urbanized society in a valley that had only one paved road and no electricity or telephones.