IWHS serves a mostly rural area that includes most of northeastern Hancock County and extends into parts of Henderson and McDonough Counties, covering the cities of Carthage, Dallas City, and La Harpe, and the village of Ferris.

IWHS was established in 2007 as a convergence of Carthage, Dallas City, and La Harpe High Schools and is housed at the former Carthage High School.

In 2009 Illini West High School did not make Adequate Yearly Progress, with 48% of students meeting standards, on the Prairie State Achievement Examination, a state test that is part of the No Child Left Behind Act.

The IWHS mascot is the Chargers, symbolized by a horse, with school colors of navy blue and orange.

The school has 4 state championships on record in team athletics and activities, Boys Football in 2008-2009 (3A) and 2010-2011 (3A), Bass Fishing in 2010, Girls Track 2015 (1A), and Boys Track 2017 (1A).