Settler colonialism, a process by which settlers take control of and transform both the land and people who live in a region into the settlers’ image, was a defining force in Oklahoma’s formation and remains pervasive in Oklahoman memory. To contextualize the idea’s impact in Oklahoma history, this thesis explores settler colonialism’s expressions on the Southern Great Plains, such as the Boomer movement - a fanatical settler colony based in Wichita, Kansas. The Boomers were at heart a settler colonial organization, but they were not unique. Hundreds of smaller colonies attempted to seize land in Indian Territory (modern day Oklahoma) between 1879 and 1901; in examining these organizations through the lens of settler colonialism, it is clear that the impact of the Boomers must be balanced within the broader context of settler colonialism on the Southern Plains; that Indigenous people in Indian Territory shaped the forces of settler colonialism; that the Boomers and their compatriots largely failed to make their dreams into a legal reality; that the subsequent state of Oklahoma Territory was fundamentally a far more aggressive settler colonial institution than the Boomers; and that settler colonialism remains an extremely pervasive force in Oklahoman identity and thought. To undo the historiographical and memorial damage created by settler colonialism in Oklahoma, a complete autopsy of the Boomers, Oklahoma history, and Southern Plains settler colonialism is necessary.