National Register of Historic Places in Stanislaus County
La Grange Gold Mines, Inc., was incorporated in 1933. In 1935, the name was changed to Tuolumne Gold Dredging Company. The gold dredge was built in 1937 for $600,000.
The scheme was to leave the flowing river bed to search for gold left in channels the river had abandoned. To do this, the dredge had to move its own pond with it, dredging ahead of itself and leaving them pond filled with tailings behind.
The dredge worked in a semi-circle, revolving around the spud anchor, which was at the stern. After the full available radius had been dredged, the great spud was lifted, the machine inched forward, and the spud was dropped again. The digging continued day and night except for brief maintenance shutdowns.
The Tuolumne dredge met misfortune about a year after it began dredging when it flipped on its side in its pond. A number of photographs of the accident have been preserved, but the machine was righted and continued working until 1949. On another occasion, the machine dug too close to a former mine tunnel, and its portable pond drained away. The pond was restored with a dike.
Inside, the dredge was a gold refinery. The gold-laden soil and rocks were first washed down in a revolving drum called a "trommel". This separated the large materials from the fine , and the fine then were sifted over a drain board. The gold, eventually was extracted by the addition of mercury, and the residue rock and soil was conveyed out the back into rows of tailing heaps which still occupy much of the river bottom.
Excerpted from the NRHP nomination dated 25 January 1971.
The marker reads:
Tuolumne Gold Dredge
Behind this monument rests the historic Tuolumne Gold Dredge which started operation at Patricksville, just east of this location, on June 15, 1938. A Walter Johnson No. 52 Model, it floated on a self-created pond of water. It was larger than a football field, weighed over 2500 tons, and cost $543,148 to construct. The dredge used electricity to drive 120 4000 lb. buckets 70 ft. deep to recover gold. It ceased operation in July 1951. The total amount of gold recovered is unknown.
Dedicated April 20, 1996
Noble Grand Humbug
Estanislao Chapter No. 58
E Clampus Vitus
A historical marker for the La Grange Gold Dredging Company Camp is located on the other side of the Tuolumne River.