By 1870 what type of organization had taken over mining in the American West?

By 1870, large-scale corporations had taken over mining operations in the American West. Initially, the mining industry started with individual prospectors who participated in the early gold and silver rushes, such as the California Gold Rush starting in 1849. These prospectors often worked alone or in small groups and used simple techniques like panning for gold. However, as surface deposits became exhausted, deeper and more complex mining operations were needed.

As the easy-to-reach placer deposits were mined out, and knowledge about geology and metallurgy advanced, mining required more capital, intricate machinery, and infrastructure, such as railroads to transport the ore and heavy equipment to dig and process it. Consequently, the cost and expertise needed for such operations were beyond the reach of individual miners or small partnerships.

This need for large investments led to the formation of corporations, which could amass capital from multiple investors. These corporations had the necessary resources to invest in advanced technologies, hire workers, and manage large-scale operations that included deep shaft mining and hydraulic mining techniques.