[2] Knox County comprises the Galesburg, IL Micropolitan Statistical Area.

In 1790, the land of the Indiana Territory that was to become Illinois was divided into two counties: St. Clair and Knox.

[5] As of the 2010 United States census, there were 52,919 people, 21,535 households, and 13,324 families residing in the county.

It leaned Whig during its early elections – although giving a plurality to Franklin Pierce in 1852 – and become powerfully Republican following that party's formation.

Although Knox did support Progressive Theodore Roosevelt against conservative incumbent President William Howard Taft in 1912, it was Franklin D. Roosevelt’s 1932 landslide before Knox County again gave the Democratic Party so much as a plurality, and it did not give a Democratic absolute majority until Lyndon B. Johnson gained such against the anti-Yankee, Southern-leaning Barry Goldwater in 1964.

The 2016 election, in the shadow of high unemployment in the “Rust Belt” saw a swing of over twenty percentage points to Donald Trump, who became the first Republican victor in the county since Ronald Reagan in 1984.