1860 – The town of Picacho sprouts up, it quickly grows to a population of 300 people. Antonio Urruttia files a claim on the Mexican Mine, now known as the Del Mexico Mine.
1861 – William H. Brewer, a member of the California Geological Survey, draft the first known description of New Idria when he visits the area with other members of the survey team. Brewer noted that between 250 to 300 men, employed in various occupations, work at the mines. Although their daily income ranges to as high as twenty-five dollars, the average wage was only three dollars. The wide variance in daily income results from the miners being paid by the job.
1867 – School opens at New Idria
1867 – The Chileanos set up a small community on a flat on the side of the mountain between New Idria and Aurora. It is called Chileano Camp, latter to become known as Mexican Flat.
1867, November – The first thirty miles of road leading from New Idria are made a public road by the Fresno County Board of Supervisors.
1868 – The Clear Creek Mine opens nearby.
1868, January – With 450 men working the mine, production peaks at 12,180 flasks, valued at $559,062, a record that will hold until World War II.
1868 – Some Mexican miners formed the "Union Méxicana" to generate enough money to work a nearby quicksilver site which they had discovered. The union sold one-half of the site to an individual who was willing to invest in the mine. This may have the Del Mexico Mine located a few miles southeast of New Idria.
1869 – The New Idria Post Office opens.
