Hancock County is part of the Fort Madison-Keokuk, IA-IL-MO Micropolitan Statistical Area.

Hancock County was part of the "Military Tract" set aside by Congress to reward veterans of the War of 1812.

Actual settlement of the interior of the county was delayed by concerns about hostile American Indians.

[3] For a brief period in the 1840s Hancock had one of Illinois' most populous cities: Nauvoo, which was then headquarters for the Church of Jesus Christ of Latter Day Saints.

The movement's founder Joseph Smith was killed in the county seat of Carthage in 1844.

In 1833 the state commissioned the formation of the county seat at Carthage, which was centrally located but not well developed.

[5] As of the 2010 United States census, there were 19,104 people, 8,040 households, and 5,427 families residing in the county.

[13] Hancock County is in Illinois's 15th Congressional District and is currently represented by Republican Mary Miller.

The county is in the 47th district of the Illinois Senate, and is represented by Republican Jil Tracy.