It was named in honor of Richard Montgomery, an American Revolutionary War general killed in 1775 while attempting to capture Quebec City, Canada.

[6] Litchfield Municipal Airport is located in Montgomery County, two nautical miles (3.7 km) southwest of the central business district of Litchfield, Illinois.

As of the 2010 United States census, there were 30,104 people, 11,652 households, and 7,806 families living in the county.

There were 13,080 housing units at an average density of 18.6 per square mile (7.2/km2).

[13] In terms of ancestry, 27.8% were German, 11.2% were Irish, 10.1% were English, and 9.8% were American.