The transition of ownership in 1864 was one of the most expensive and complex land-title litigation in 19th-century America.
Overlapping Claims: The Core of the Dispute centered on two conflicting types of land rights: 1. Castillero’s original 1845 claim (later held by Barron, Forbes & Co.) was based on Mexican mining laws; and 2. The surrounding land was part of Rancho Los Capitancillos. The owners of the Rancho argued that since the mine was on their property, the minerals belonged to them under U.S. law, despite the earlier Mexican mining grant.
The "Lincoln Writ": By 1863, the case had reached the U.S. Supreme Court (United States v. Castillero). The Court eventually ruled against Barron, Forbes & Co., declaring Castillero’s original title invalid due to technicalities in how the Mexican officials had processed the paperwork. Seeing an opportunity to secure mercury—a "strategic mineral" used for gold processing and percussion caps for the Union Army— President Abraham Lincoln issued an executive order to seize the mine for the government.
The Standoff: When federal marshals arrived in San Jose to enforce the seizure, the mine's managers threatened to flood the shafts and destroy the equipment. Fearing that a "second front" of the Civil War might break out in California, Lincoln eventually rescinded the order.
The Quicksilver Mining Company: Without legal standing and the threat of federal seizure looming, Barron, Forbes & Co. were backed into a corner. The Quicksilver Mining Company of New York (QMC), a well-funded Eastern syndicate that had been fighting for the title from a different legal angle, stepped in. In 1864, they paid $1.75 million to buy out the interests of Barron, Forbes & Co. and the competing Rancho claimants. This consolidated all titles under one American corporation, ending nearly 20 years of "bitter legal battles."