It's not obvious from the title, but Stephen Aron's American Confluence: The Missouri Frontier from Borderland to Border State (Bloomington & Indianapolis: Indiana University Press, 2006) is part of the series including Frontier Indiana, Frontier Illinois, The Ohio Frontier, and The Wisconsin Frontier. Aron recognized that the story starts, not with what-later-became-the-state-of-Missouri, but with the important confluence of rivers from the Missouri-Mississippi down to the Mississippi-Ohio, and surrounding territory.
One key theme here is a rethinking of the frontier and white-Indian relations based on Richard White's wonderful 1991 classic The Middle Ground: Indians, Empires, and Republics in the Great Lakes Region, 1650-1815. None of the governments or tribes that purported to rule the proto-Midwest had power to make their wishes law in day-to-day life, so what actually happened was the result of local negotiations and creative misunderstandings among different cultures. As long as European states and empires competed for the land, Indians had room to maneuver and play one group off against another. After the War of 1812, however, they had only one country to deal with, and its white inhabitants rarely respected other races (although comparatively enlightened leaders like Meriwether Lewis and William Clark tried to do so). Time and again the following pattern was repeated:
Lured again by exuberant descriptions of the region's fertility, increasing numbers of squatters entered the supposedly off-limits area [reserved for Indians, often refugees from further east], then complained about Indian depredations and pressed the government to oust the Indians and confirm their holdings.
Even tribes that were assimilating to European ways of settled agriculture had land stolen from them in this way. Genealogist who take the word of "old settlers" about hostile Indians are likely to be seriously misled about what actually happened back then on the frontier.