The story of Tishomingo is set against a backdrop of Indian Territory in the late 1890's. It centers on the people of the Chickasaw Nation, their way of life, politics and assimilation before Oklahoma statehood. As the story unfolds, we follow Koi, a beautiful mixed-blood Chickasaw girl, as she grows into womanhood in Tishomingo, Indian Territory. Koi is in love with her childhood friend, Osi, a full-blood Chickasaw with whom she grew up. One day her life is forever changed with the arrival of Neville Cooper, a white man contracted by the federal government to conduct a census of the Five Civilized Tribes. His visit was like a stone dropped into the quiet waters of Pennington Creek, rippling outward to change the course of not only her life but everyone around her, in ways that none of them could have anticipated.