Missouri's history as a frontier territory reveals a story of overlapping colonial claims, violent border conflicts, and cultural collisions that shaped the character of a state and influenced the trajectory of American westward expansion. For decades, three different flags flew over Missouri territory as French, Spanish, and American powers competed for control of the strategically vital confluence of the Mississippi and Missouri rivers, and the human consequences of those competing claims were often brutal. The French were the first Europeans to establish a significant presence in the region, building trading posts and missions along the river systems that served as the highways of the colonial interior. French colonists developed relationships with Indigenous nations based primarily on trade rather than territorial displacement, creating a front ...