Till and outwash from the Illinoian glaciation covers area bedrock to a depth of several hundred feet.

By the time of the first identified human settlements, the region was made up of thickly wooded forested hills and grassy prairie plains.

Archeological study at the Koster Site seems to indicate that humans had established complex societies ten thousand years ago along the river basins of the Illinois and Mississippi.

By the time of European exploration, Upper Mississippian culture collapsed; westward expansion forced many Algonquin-speaking nations into conflict with each other as they moved after encroachment of their lands.

Potowatomi and Mascouten tribes were still living in the region when white settlers arrived and statehood was declared in 1818.

They arrived as a result of the end of the Black Hawk War as well as the completion of the Erie Canal.

These were "Yankee" settlers, that is to say they were descended from the English Puritans who settled New England in the colonial era.

They were primarily members of the Congregational Church though due to the Second Great Awakening many of them had converted to Methodism and some had become Baptists before coming to what is now Boone County.

When the New England settlers arrived in what is now Boone County there was nothing but a dense virgin forest and wild prairie.

The candidacy of Ross Perot in 1992 and 1996 caused George H. W. Bush and Bob Dole both to win Boone County with mere pluralities against Bill Clinton, and in 2008, Illinois resident Barack Obama became the only Democrat to carry the county since James K. Polk in 1844.