[2] The Dixon, IL Micropolitan Statistical Area includes all of Lee County.

[3] The early nineteenth century saw a wave of westward movement from New England, due largely to completion of the Erie Canal and the end of the Black Hawk War.

It is largely understood that the county's name honors "Lighthorse Harry" Lee, an officer in the American Revolutionary War.

[6] An alternative theory suggests the name honors Richard Henry Lee, a member of the Continental Congress (the Declaration of Independence was adopted pursuant to the Lee Resolution).

[9] As of the 2010 United States Census, there were 36,031 people, 13,758 households, and 9,064 families residing in the county.

It is one of very few counties in the United States to have never supported a Democrat for President since the Civil War.

The only occasion when the Republican candidate did not win the county in this time was in 1912, when Theodore Roosevelt carried it while running as a member of the Progressive Party, unofficially known as the "Bull Moose" party.