The Quincy Mine was founded in 1846 by the merger of the Northwest Mining Company and the Portage Mining Company. Due to poor communication between government offices, these two speculative mining companies had purchased the same tracts of land during the mining rush of the early 1840s. The directors met and decided to merge, with significant investment coming from Massachusetts (the town of Quincy, Massachusetts lent the mine its name). While many other copper mines were founded at the same time, the Quincy Mine became the most successful of the 1840s-era mines, and was the country's leading copper-producing mine from 1863 (when it exceeded the production of the Minesota Mine) through 1867 (after which it was exceeded by the Calumet and Hecla).
The mine was the first Michigan copper mine to switch from fissure mining to amygdaloid mining, when the recently discovered Pewabic amygdaloid lode was found to cross Quincy property in 1856. High-grade fissure veins contained large, pure masses of copper, but the masses could take days or even months to extract, at high cost. Amygdaloid mining consisted of extracting lower-grade strataform orebodies in the "amygdaloid zones," the upper portions of basalt lava flows. Rock bearing small pockets of copper could be blasted out immediately and processed elsewhere at much lower cost. Amygdaloid mining proved much more productive than fissure mining, and the size and richness of the Pewabic lode in particular allowed the Quincy to produce profits for 53 consecutive years. The Quincy company expanded laterally along the lode by buying out adjacent properties. The company bought the Pewabic mine in 1891, the Mesnard and the Pontiac in 1897, and the Franklin mine in 1908. This helped the mine survive longer than almost all other Keweenaw copper mining companies, except the Calumet and Hecla Mining Company and the Copper Range Company.
To attract a better class of worker, the Quincy Mining Company built and maintained housing for the workers. Over the course of operations, the types of housing ranged from simple tents in the early days, to complete three story houses shortly before the mine's shutdown. The executives on the east coast wanted to build more elaborate and fancy homes with amenities such as electricity and running water. However, the on-site managers didn't think it was necessary for the miners to have such high-class dwellings. But the east coast executives realized that if they offered nicer homes to the workers, the miners were more likely to stay, raise families, and be less likely to leave the area or transfer to another mining company. This strategy proved effective and helped the Quincy Mining Company retain its status as one of the premier mining companies in the region.
The Quincy Mining Company closed operations (but did not dissolve) in 1931 due to low copper prices. During World War II, the mines re-opened due to increased copper demand. When the government stopped supporting copper prices after the war, the mines quickly closed for good.