What was one of the main economic motivations for the USA to fight the 'Indian Wars' between 1865 to 1890?

The primary economic motivation for the United States to engage in the 'Indian Wars' from 1865 to 1890 was the desire to access gold and mineral resources. During this period, significant gold and mineral discoveries were made in territories traditionally inhabited by Native American tribes, such as the Black Hills of South Dakota and other regions in the West. This led to an influx of settlers and miners, intensifying the demand for land that was held by Native Americans.

As prospectors flooded into these areas in search of wealth, the U.S. government promoted policies that facilitated the removal of Native Americans from their ancestral lands. The government aimed to secure these territories for American settlers and businesses, believing that access to these resources would bolster the U.S. economy and enhance its global standing. The combination of economic opportunity and the ideology of Manifest Destiny—belief in the expansion of the U.S. across the continent—fueled conflict with Indigenous peoples, leading to the Indian Wars of this era.

In this context, while expansion of railroads and creation of agricultural land were also significant developments during this time, they were part of the broader goals associated with economic growth. However, the immediate trigger for many of the conflicts was primarily focused on gaining access to valuable