To banish forever : a secret society, the Ho-Chunk, and ethnic cleansing in Minnesota / Cathy Coats.

Enhanced descriptions from Syndetics:

The largely untold story of the Ho-Chunk exile from Minnesota, in which local white residents sought to expel all indigenous people from the region and deny Native claims to some of the richest farmland in the world.

In 1863, after the end of the US-Dakota War, a group of men in Mankato, Minnesota, formed a secret society. At the beginning of every meeting, members of the Knights of the Forest recited its ritual pledge, including these words: "I sincerely hope this meeting may be profitable to each one of us, and that we may go forth from this Lodge stronger and braver in the determination to banish forever from our beautiful State every Indian who now desecrates our soil."

The Ho-Chunk people, who had not participated in the war, occupied a reservation about two miles south of Mankato on some of the state's richest agricultural lands. The Knights--determined to claim these lands for their own profit--advocated for the removal of the Ho-Chunk, who had already been forced to move three times before settling in Blue Earth County of south-central Minnesota. Exploiting the fears of white people living in the area at the end of the brutal war, the Knights sent armed men to surround the Ho-Chunk reservation, threatening to shoot anyone who crossed the line. Within just a few years, the Ho-Chunk had been kicked off their land and removed to reservations outside of the state.

This is the story of the Knights, the Ho-Chunk, and the ethnic cleansing of southern Minnesota.