[1] Its county seat is Macomb,[2] which is also the home of Western Illinois University.

McDonough County is part of the Macomb, IL Micropolitan Statistical Area.

McDonough County is named in honor of Thomas Macdonough who defeated a British squadron in the decisive naval Battle of Lake Champlain in the War of 1812.

[3] McDonough County was part of the "Military Tract" set aside by Congress for veterans of the War of 1812.

[4] The county has the unusual distinction of forming a perfect square by Mercator map projection.

[5] As of the 2010 United States census, there were 32,612 people, 13,057 households, and 6,724 families residing in the county.

The cities of Colchester, Industry, Good Hope, Sciota, and Adair are currently represented by Republican Norine Hammond of the 94th district.